This work was supported by the Natural Sciences and Engineering Research Council of Canada.

1. Obtaining Genes of Interest
<ol>
	<li>Design synthetic genes.
	<ol>
		<li>Optimize a gene sequence for E. coli expression.</li>
		<li>Remove any problematic restriction sites from the sequence (AvrII, NdeI, EcoRI, and XbaI).</li>
		<li>Incorporate restriction sites for cloning; a 5&#8242;-NdeI site and a 3&#8242;-EcoRI site are recommended. Other sites can be used, if necessary; refer to the multicloning region of the selected plasmid (Figure S1-S4</str...

<ol>
	<li>Purnick, P. E. M., Weiss, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+second+wave+of+synthetic+biology:+from+modules+to+systems.">The second wave of synthetic biology: from modules to systems.</a> Nat. Rev. Mol. Cell Biol. 10 (6), 410-422 (2009).</li><li>Bieniossek, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automated+unrestricted+multigene+recombineering+for+multiprotein+complex+production.">Automated unrestricted multigene recombineering for multiprotein complex production.</a> Nat. Methods. 6 (6), 447-450 (2009).</li><li>Jochimsen, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Five+phosphonate+operon+gene+products+as+components+of+a+multi-subunit+complex+of+the+carbon-phosphorus+lyase+pathway.">Five phosphonate operon gene products as components of a multi-subunit complex of the carbon-phosphorus lyase pathway.</a> Proc. Natl. Acad. Sci. USA. 108 (28), 11393-11398 (2011).</li><li>Martin, V. J. J., Pitera, D. J., Withers, S. T., Newman, J. D., Keasling, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+a+mevalonate+pathway+in+Escherichia+coli+for+production+of+terpenoids.">Engineering a mevalonate pathway in Escherichia coli for production of terpenoids.</a> Nat. Biotechnol. 21 (7), 796-802 (2003).</li><li>Ajikumar, P. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isoprenoid+pathway+optimization+for+Taxol+precursor+overproduction+in+Escherichia+coli.">Isoprenoid pathway optimization for Taxol precursor overproduction in Escherichia coli.</a> Science. 330 (6000), 70-74 (2010).</li><li>Boddy, C. N., Hotta, K., Tse, M. L., Watts, R. E., Khosla, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Precursor-directed+biosynthesis+of+epothilone+in+Escherichia+coli.">Precursor-directed biosynthesis of epothilone in Escherichia coli.</a> J. Am. Chem. Soc. 126 (24), 7436-7437 (2004).</li><li>Lundgren, B. R., Boddy, C. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sialic+acid+and+N-acyl+sialic+acid+analog+production+by+fermentation+of+metabolically+and+genetically+engineered+Escherichia+coli.">Sialic acid and N-acyl sialic acid analog production by fermentation of metabolically and genetically engineered Escherichia coli.</a> Org. Biomol. Chem. 5 (12), 1903-1909 (2007).</li><li>Horsman, M. E., Lundgren, B. R., Boddy, C. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=N-Acetylneuraminic+Acid+Production+in+Escherichia+coli+Lacking+N-Acetylglucosamine+Catabolic+Machinery.">N-Acetylneuraminic Acid Production in Escherichia coli Lacking N-Acetylglucosamine Catabolic Machinery.</a> Chem. Eng. Commun. 203 (10), 1326-1335 (2016).</li><li>Romier, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Co-expression+of+protein+complexes+in+prokaryotic+and+eukaryotic+hosts:+experimental+procedures,+database+tracking+and+case+studies.">Co-expression of protein complexes in prokaryotic and eukaryotic hosts: experimental procedures, database tracking and case studies.</a> Acta Crystallogr. D, Biol. Crystallogr. 62 (Pt 10), 1232-1242 (2006).</li><li>Tolia, N. H., Joshua-Tor, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Strategies+for+protein+coexpression+in+Escherichia+coli.">Strategies for protein coexpression in Escherichia coli.</a> Nat. Methods. 3 (1), 55-64 (2006).</li><li>Chanda, P. K., Edris, W. A., Kennedy, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+set+of+ligation-independent+expression+vectors+for+co-expression+of+proteins+in+Escherichia+coli.">A set of ligation-independent expression vectors for co-expression of proteins in Escherichia coli.</a> Protein Expr. Purif. 47 (1), 217-224 (2006).</li><li>Kim, K. -. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-promoter+vector+is+highly+efficient+for+overproduction+of+protein+complexes.">Two-promoter vector is highly efficient for overproduction of protein complexes.</a> Protein Sci. 13 (6), 1698-1703 (2004).</li><li>Tan, S., Kern, R. C., Selleck, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+pST44+polycistronic+expression+system+for+producing+protein+complexes+in+Escherichia+coli.">The pST44 polycistronic expression system for producing protein complexes in Escherichia coli.</a> Protein Expr. Purif. 40 (2), 385-395 (2005).</li><li>Chen, X., Pham, E., Truong, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TEV+protease-facilitated+stoichiometric+delivery+of+multiple+genes+using+a+single+expression+vector.">TEV protease-facilitated stoichiometric delivery of multiple genes using a single expression vector.</a> Protein Sci. 19 (12), 2379-2388 (2010).</li><li>Lorenz, T. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polymerase+chain+reaction:+basic+protocol+plus+troubleshooting+and+optimization+strategies.">Polymerase chain reaction: basic protocol plus troubleshooting and optimization strategies.</a> J. Vis. Exp. (63), e3998 (2012).</li><li>Lee, P. Y., Costumbrado, J., Hsu, C. -. Y., Kim, Y. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Agarose+gel+electrophoresis+for+the+separation+of+DNA+fragments.">Agarose gel electrophoresis for the separation of DNA fragments.</a> J. Vis. Exp. (62), (2012).</li><li>Sukumaran, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Concentration+determination+of+nucleic+acids+and+proteins+using+the+micro-volume+BioSpec-nano-spectrophotometer.">Concentration determination of nucleic acids and proteins using the micro-volume BioSpec-nano-spectrophotometer.</a> J. Vis. Exp. (48), (2011).</li><li>JoVE Science Education Database. Basic Methods in Cellular and Molecular Biology. Molecular Cloning. J. Vis. Exp Available from: <a target="_blank" href="https://www.jove.com/science-education/5074/molecular-cloning">https://www.jove.com/science-education/5074/molecular-cloning</a> (2016)</li><li>JoVE Science Education Database. Basic Methods in Cellular and Molecular Biology. The Western Blot. J. Vis. Exp Available from: <a target="_blank" href="https://www.jove.com/science-education/5065/the-western-blot">https://www.jove.com/science-education/5065/the-western-blot</a> (2016)</li><li>Laible, M., Boonrod, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Homemade+site+directed+mutagenesis+of+whole+plasmids.">Homemade site directed mutagenesis of whole plasmids.</a> J. Vis. Exp. (27), (2009).</li></ol>

Co-expression of multiple genes is increasingly essential, particularly in characterizing and reconstituting complex, multigene metabolic pathways3,4,5. The pMGX system makes multigene co-expression in E. coli routine6,7,8 and accessible to diverse researchers. In this study, five proteins of interest were shown to be simultane...

Co-expression of multiple proteins is increasingly essential, particularly in synthetic biology applications, where multiple functional modules must be expressed1; in studying protein-protein complexes, where expression and function often require co-expression2,3; and in characterizing and harnessing biosynthetic pathways, where each gene in the pathway must be expressed4,5,6,7,8. A number of systems have been developed for co-expression, particularly in the host organism Escherichia coli, the work horse for laboratory recombinant protein expression9. For example, multiple plasmids with differing selectable markers can be used to express individual proteins using a wealth of different expression vectors10,11. Single plasmid systems for multiple protein expression have used either multiple promoters to control the expression of each gene10,12; synthetic operons, where multiple genes are encoded on a single transcript2,13; or, in some cases, a single gene encoding a polypeptide that is ultimately proteolytically processed, yielding the desired proteins of interest14.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/55187/55187fig1.jpg" /> 
Figure 1: pMGX workflow showing the construction of a polycistronic vector. The pMGX system provides a flexible, easy-to-use strategy for the construction of synthetic operons under the control of an inducible T7 promoter. <a href="//cloudflare.jove.com/files/ftp_upload/55187/55187fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
In this manuscript, the use of a highly effective system for the construction of multigene synthetic operons under the control of an inducible T7 RNA polymerase (Figure 1) is described. This system allows many genes to be expressed simultaneously from one plasmid. It is based on a plasmid system, originally called pKH22, that has been used successfully for a number of different applications6,7,8. Here, this plasmid set is expanded to include four related vectors: pMGX-A, an expression vector lacking any C- or N-terminal tags and with the ampicillin resistance marker; pMGX-hisA, an expression vector encoding an N-terminal hexahistidine tag and with the ampicillin resistance marker; pMGX-K, an expression vector lacking any C- or N-terminal tags and with the kanamycin resistance marker; and pMGX-hisK, an expression vector encoding an N-terminal hexahistidine tag and with the kanamycin resistance marker. In this study, the method for generating a polycistronic vector containing five genes using the pMGX system, specifically pMGX-A, is demonstrated along with the successful production of each individual protein in Escherichia coli.

<table border="0" cellpadding="0" cellspacing="0" width="1224">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:327px;">Enzymes</td>
			<td style="width:312px;"></td>
			<td style="width:139px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Alkaline Phosphatase, Calf Intestinal (CIP)</td>
			<td style="width:312px;">New England Biolabs</td>
			<td style="width:139px;">M0290S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">AvrII</td>
			<td style="width:312px;">New England Biolabs</td>
			<td style="width:139px;">R0174S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">EcoRI</td>
			<td style="width:312px;">New England Biolabs</td>
			<td style="width:139px;">R0101S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NdeI</td>
			<td style="width:312px;">New England Biolabs</td>
			<td style="width:139px;">R0111S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">XbaI</td>
			<td style="width:312px;">New England Biolabs</td>
			<td style="width:139px;">R0145S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Herculase II Fusion DNA Polymerase</td>
			<td style="width:312px;">Agilent Technologies</td>
			<td style="width:139px;">600677</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">T4 DNA Ligase</td>
			<td style="width:312px;">New England Biolabs</td>
			<td style="width:139px;">M0202S</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:327px;">Name</td>
			<td style="width:312px;">Company</td>
			<td style="width:139px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:327px;">Reagents</td>
			<td style="width:312px;"></td>
			<td style="width:139px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1 kb DNA ladder</td>
			<td style="width:312px;">New England Biolabs</td>
			<td style="width:139px;">N3232L</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">4-20% Mini-PROTEAN TGX Stain-Free Protein Gels</td>
			<td style="width:312px;">Bio-Rad</td>
			<td style="width:139px;">456-8095</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">50 x TAE</td>
			<td style="width:312px;">Fisher Thermo Scientific</td>
			<td style="width:139px;">BP1332-4</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Agar</td>
			<td style="width:312px;">Fisher Thermo Scientific</td>
			<td style="width:139px;">BP1423-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Agarose</td>
			<td style="width:312px;">Fisher Thermo Scientific</td>
			<td style="width:139px;">BP160-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ampicilin</td>
			<td style="width:312px;">Sigma-Alrich</td>
			<td style="width:139px;">A9518-5G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">BL21 (DE3) chemically comeptent cells</td>
			<td></td>
			<td style="width:139px;"></td>
			<td style="width:448px;">Comeptent cell prepared in house</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">B-PER Bacterial Protein Extraction Reagent</td>
			<td style="width:312px;">Fisher Thermo Scientific</td>
			<td>PI78243</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">dNTP mix</td>
			<td style="width:312px;">Agilent Technologies</td>
			<td style="width:139px;"></td>
			<td>Supplied with polymerase</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Gel Extraction Kit</td>
			<td style="width:312px;">Omega</td>
			<td style="width:139px;">D2500-02</td>
			<td>E.Z.N.A Gel Extraction, supplied by VWR Cat 3: CA101318-972</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glycine</td>
			<td style="width:312px;">Fisher Thermo Scientific</td>
			<td style="width:139px;">BP381-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">His Tag Antibody [HRP], mAb, Mouse</td>
			<td style="width:312px;">GenScript</td>
			<td style="width:139px;">A00612</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Immobilon Western Chemiluminescent HRP Substrate</td>
			<td style="width:312px;">EMD Millipore</td>
			<td style="width:139px;">WBKLS0100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">IPTG</td>
			<td style="width:312px;">Sigma-Alrich</td>
			<td style="width:139px;">15502-10G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LB</td>
			<td style="width:312px;">Fisher Thermo Scientific</td>
			<td style="width:139px;">BP1426-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Methanol</td>
			<td style="width:312px;">Fisher Thermo Scientific</td>
			<td style="width:139px;">A411-20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Pasteurized instant skim milk powder</td>
			<td style="width:312px;">Local grocery store</td>
			<td style="width:139px;"></td>
			<td>No-name grocery store milk is adequate</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Nitrocellulose membrane</td>
			<td style="width:312px;">Amersham Protran (GE Healthcare Life Sciences)</td>
			<td style="width:139px;">10600007</td>
			<td>Membrane PT 0.45 &#181;m 200 mm X 4 m, supplied by VWR Cat #: CA10061-086</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Plasmid DNA Isolation Kit</td>
			<td style="width:312px;">Omega</td>
			<td style="width:139px;">D6943-02</td>
			<td>E.Z.N.A Plasmid DNA MiniKit I, supplied by VWR Cat #: CA101318-898</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">pMGX</td>
			<td style="width:312px;">Boddy Lab</td>
			<td style="width:139px;"></td>
			<td>Request from the Boddy Lab Contact cboddy@uottawa.ca</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Primers</td>
			<td style="width:312px;">Intergrated DNA Technologies</td>
			<td style="width:139px;"></td>
			<td>Design primers as needed for desired gene</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Synthetic Gene</td>
			<td style="width:312px;">Life Technologies</td>
			<td style="width:139px;"></td>
			<td>Design and optimize as needed</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Thick Blot Filter Paper</td>
			<td style="width:312px;">Bio-Rad</td>
			<td style="width:139px;">1703932</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tris base</td>
			<td style="width:312px;">BioShop</td>
			<td style="width:139px;">TRS001.1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tween-20</td>
			<td style="width:312px;">Sigma-Alrich</td>
			<td style="width:139px;">P9416-50ML</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">XL1-Blue chemically competent cells</td>
			<td></td>
			<td style="width:139px;"></td>
			<td style="width:448px;">Comeptent cell prepared in house</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:327px;">Name</td>
			<td style="width:312px;">Company</td>
			<td style="width:139px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:327px;">Equipment</td>
			<td style="width:312px;"></td>
			<td style="width:139px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">BioSpectrometer</td>
			<td style="width:312px;">Eppendorf</td>
			<td style="width:139px;">RK-83600-07</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Gel box - PAGE</td>
			<td style="width:312px;">Bio-Rad</td>
			<td style="width:139px;">1658005</td>
			<td>Mini-PROTEIN Tetra Vertical Electrophoresis Cell</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Gel Imager</td>
			<td style="width:312px;">Alpha Innotech</td>
			<td style="width:139px;"></td>
			<td>AlphaImager EC</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Incubator-oven</td>
			<td style="width:312px;">Fisher Thermo Scientific</td>
			<td style="width:139px;">11-690-650D</td>
			<td>Isotemp</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Incubator-shaker</td>
			<td style="width:312px;">Fisher Thermo Scientific</td>
			<td style="width:139px;">SHKE6000-7</td>
			<td>MaxQ 6000</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Personna Razors</td>
			<td style="width:312px;">Fisher Thermo Scientific</td>
			<td style="width:139px;">S04615</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Power Pack</td>
			<td style="width:312px;">Bio-Rad</td>
			<td style="width:139px;">S65533Q</td>
			<td>FB300</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Transilluminator</td>
			<td style="width:312px;">VWR International</td>
			<td style="width:139px;">M-10E,6W</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Thermocylcer</td>
			<td style="width:312px;">Eppendorf</td>
			<td>Z316091</td>
			<td>Mastercycler Personal, supplied by Sigma</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">UV Face-Shield</td>
			<td style="width:312px;"></td>
			<td style="width:139px;">18-999-4542</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Waterbath</td>
			<td style="width:312px;">Fisher Thermo Scientific</td>
			<td style="width:139px;">15-460-2SQ</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Western Transfer Apparatus</td>
			<td style="width:312px;">Bio-Rad</td>
			<td style="width:139px;">1703935</td>
			<td>Mini-Trans Blot Cell</td>
		</tr>
	</tbody>
</table>

inducible t7 rna polymerase-mediated multigene expression system, pmgx

Co-expression of multiple proteins is increasingly essential for synthetic biology, studying protein-protein complexes, and characterizing and harnessing biosynthetic pathways. In this manuscript, the use of a highly effective system for the construction of multigene synthetic operons under the control of an inducible T7 RNA polymerase is described. This system allows many genes to be expressed simultaneously from one plasmid. Here, a set of four related vectors, pMGX-A, pMGX-hisA, pMGX-K, and pMGX-hisK, with either the ampicillin or kanamycin resistance selectable marker (A and K) and either possessing or lacking an N-terminal hexahistidine tag (his) are disclosed. Detailed protocols for the construction of synthetic operons using this vector system are provided along with the corresponding data, showing that a pMGX-based system containing five genes can be readily constructed and used to produce all five encoded proteins in Escherichia coli. This system and protocol enables researchers to routinely express complex multi-component modules and pathways in E. coli.

In this study, the goal was to co-express five proteins from a single plasmid. The five-codon optimized synthetic gene fragments encoding either N- or C-terminal hexahistidine tags were purchased commercially. The synthetic genes were amplified by PCR and individually cloned into a PCR-blunt vector and sequenced. To generate the polycistronic plasmid, the five genes of interest were first cloned into a suitable pMGX plasmid, pMGX-A. Figure 2 shows PCRBlunt-<e...

Watch this Scientific Journal Video about Inducible T7 RNA Polymerase-mediated Multigene Expression System, pMGX at JoVE.com

Inducible T7 RNA Polymerase-mediated Multigene Expression System, pMGX

This study describes methods for the T7-mediated co-expression of multiple genes from a single plasmid in Escherichia coli using the pMGX plasmid system.

Co-expression of multiple proteins is increasingly essential for synthetic biology, studying protein-protein complexes, and characterizing and harnessing ...

The overall goal of this procedure is to construct multigene synthetic operons under the control of an inducible T7 RNA polymerase for expressing multiple proteins simultaneously. This method can help researchers in synthetic biology and biochemistry, enabling them to build multi-protein pathways or study protein complexes that are dependent on co-expression multiple approaches. The main advantage of this technique is that it allows multiple genes to expressed simultaneously in Escherichia coli from a single plasma.Demonstrating the procedure from my lab, will be Mohamed Hassan, a PhD student and Angela Thompson, a Co-op student. After obtaining and amplifying genes of interest according to the text protocol, prepare digestion reactions for the first gene of interest and the pMGX factor. Using a 40 microliter reaction containing 0.5 to 1.5 micrograms of DNA into the indel enzyme.Incubate the reactions at 37 degree Celsius for one hour. Then add EcoRI and allow the digest to proceed for an additional hour. NdeI is added prior to EcoRI to ensure that it digests effectively.NdeI is sensitive to the length in double-stranded DNA on either side of the restriction site. Adding it first ensures that it cuts the full-length circular plasma. Load the digestion reactions on to a 0.7%agarose gel and electrophores the samples at 100 volts for 55 minutes.Then, with a clean scalpel or razor blade, excise the insert and vector bands and place the excise gel segments into 1.5 milliliter tubes. Use a gel extraction kit according to the text protocol to purify the DNA. Set up a 20 microliter ligation reaction containing 0.15 to 0.5 micrograms of vector DNA and appropriate amount of insert depending on the size of the gene and one microliter of T4 DNA ligase.Under aseptic conditions, thaw on ice 100 microliter aliquots of chemically competent XL1-Blue E.coli cells for five minutes. And then add five microliters of the ligation reactions containing a gene of interest to the cells. Incubate the transformations on ice for 30 minutes.Next, heat shock the cells for 45 seconds in a 42 degree Celsius water bath. Then, place the transformations on ice and then add 200 microliters of cold LB medium. Leave the cells to incubate for two minutes.Incubate the cells at 37 degree Celsius in 220 rotations per minute for one hour and spread 100 microliters onto LB agar plates containing an appropriate selectable marker. To screen colonies for possible transformants, compare the number of colonies on the negative control versus the ligation plates. A colony count ratio of one to two is desired.Select four to eight individual colonies from each ligation reaction to inoculate 4 milliliters of LB with the appropriate antibiotic. Incubate the cultures at 37 degree Celsius and 220 rotations per minute overnight. With the plasmid DNA isolation kit, purify the plasmid DNA according to the text protocol and set up 20 microliter digestion reactions with 150 to 500 nanograms of DNA using one microliter each of NdeI and EcoRI.Incubate the digestion reactions at 37 degrees Celsius for two hours. To insert gene two into the pMGX vector containing gene one, setup a 40-microliter digestion reaction containing 0.5 to 1.5 micrograms of vector DNA containing the first gene of interest and one microliter of AVR2. Incubate the reaction at 37 degrees Celsius for 1.5 hours before adding 1.5 microliters of Calf-intestinal phosphatase.Incubate for an additional 30 minutes. Next, set up a 40 microliter digestion reaction containing 0.5 to 1.5 micrograms of the pMGX vector containing the second gene of interest. Using one microliter of AVR2 and xpol.Incubate the reaction at 37 degree Celsius for two hours. Electrophoris the restriction digests on 0.7 agarose gel. And use a clean scalpel eraser to excise the insert and vector bands as demonstrated earlier.After extracting the plasmid DNA and quantifying the sample according to the text protocol, set up a ligation reaction using a 3:1 insert to vector ratio of gene 2 and pMGX-yfg1. Include a negative control using pMGX-yfg1 only. Transform five microliters of each reaction into XL1-Blue cells as demonstrated earlier.Then compare the colony count on the negative control and ligation plates. If there are a large number of colonies on the negative control plate, review the CIP treatment. Select four to eight individual colonies from the ligation reaction and use each colony to inoculate four microliter of LB plus the appropriate antibiotic.Grow at 37 degrees Celsius and 220 rotations per minute overnight. After isolating and quantifying the plasmid DNA as before, screen for effective insertion of the second gene by setting up a digestion reaction containing 150 to 500 nanograms of DNA and one microliter of EcoRI. Incubate the reactions at 37 degrees Celsius for two hours.EcoRI is recommended for screening purposes but in some cases, EcoRI may generate two or more inserts that are similar in size which are difficult to distinguish on a gel. To ensure success, alternative restriction digest enzyme such as NdeI should be used. Separate the digestion reactions on an agarose gel, looking for a band that corresponds to the size of the inserted gene 2.Clone additional genes into the plasmid according to the text protocol. To generate the polycistronic plasmid, the five genes were first cloned into a suitable plasmid, pMGX A.This figure shows pCR-Blunt-yfg1 and pCR-Blunt-yfg2 in the pMGX A plasmid as well as pMGX A digested with indel and EcoRI. To clone the first two genes into pMGX A, the plasmid was digested with indel and EcoRI.After cloning, pMGX-yfg1 and pMGX-yfg2 where digested with AVR2 and xpol to confirm that successful clones were obtained. This figure shows the pMGXyfg1 vector digested with AVR2 and the pMGX-yfg2 vector digested with AVR2 and xpol to isolate gene of interest two. The resulting insert was cloned pMGX-yfg1 to create the pMGX-yfg1 two vector.As seen here, digestion of pMGX-yfg1 two with EcoRI confirmed the successful cloning of gene interest number two into pMGX-yfg1. This gel image demonstrates the difference between digestive plasmids that either had the insert in the correct orientation or in a reverse orientation. An insert in the reverse orientation would two EcoRI sites in close proximity making the resulting digested 50 base pair fragments undetectable on the gel and the backbone larger.Finally, after generating a five-gene polycistronic expression vector, a western blot of the expressed proteins confirms that all five proteins were expressed from a single vector. Note that the protein produced by yfg5 is the same size as yfg1 and is not separated on the gel. Once mastered, this technique can be completed in three or four days for every gene inserted into pMGX backbone if it is done correctly.While attempting this procedure, it's important to remember to treat and linearize vector with the phosphatase such as Calf-intestinal phosphatase to dephosphorylate the five vector. Following this procedure, further experiments such as in vivo multigene expression can be performed in order to characterize and harness biosynthetic pathways for the production natural products or to study protein-protein complexes. This technique paved the way for researchers in the synthetic biology field to produce complex carbohydrates and genetically engineered E.Coli.After watching this video, you should have a good understanding of how to implement the multigene expressions system in E.coli.

inducible-t7-rna-polymerase-mediated-multigene-expression-system-pmgx

Research

JoVE Journal

Genetics

13.1K Aufrufe.  University of Ottawa. The overall goal of this procedure is to construct multigene synthetic operons under the control of an inducible T7 RNA polymerase for expressing multiple proteins simultaneously. This method can help researchers in synthetic biology and biochemistry, enabling them to build multi-protein pathways or study protein complexes that are dependent on co-expression multiple approaches. The main advantage of this technique is that it allows multiple genes to expressed simultaneously in Escherichia co...