This work was supported by the Japan Society for the Promotion of Science (JSPS) (grant numbers 16K15860 and 19K10471 to T. M., 17K12032 to M. I., and 18K09926 to N. H.) and the SECOM Science and Technology Foundation (SECOM) (grant number 2018.09.10 No. 1).

NOTE: Generation of S. mutans &#8710;gtfC, in which the entire coding region of the gtfC gene is replaced with spcr, must be completed prior to performing these protocols. Refer to the published article for details on generation5.
1. Primer design
<ol>
	<li>Prepare primers for the construction of S. mutans His-gtfC. 
	NOTE: The primer sequences used...

<ol>
	<li>Sambrook, J., Russell, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Molecular Cloning: A Laboratory Manual 3rd Edition. , (2001).</li><li>Murata, T., Ishikawa, M., Shibuya, K., Hanada, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Method+for+functional+analysis+of+a+gene+of+interest+in+Streptococcus+mutans:+gene+disruption+followed+by+purification+of+a+polyhistidine-tagged+gene+product.">Method for functional analysis of a gene of interest in Streptococcus mutans: gene disruption followed by purification of a polyhistidine-tagged gene product.</a> Journal of Microbiological Methods. 155, 49-54 (2018).</li><li>Horton, R. M., Cai, Z., Ho, S. M., Pease, L. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gene+splicing+by+overlap+extension:+tailor-made+genes+using+the+polymerase+chain+reaction.">Gene splicing by overlap extension: tailor-made genes using the polymerase chain reaction.</a> Biotechniques. 54 (3), 129-133 (2013).</li><li>Murata, T., Hanada, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Contribution+of+chloride+channel+permease+to+fluoride+resistance+in+Streptococcus+mutans.">Contribution of chloride channel permease to fluoride resistance in Streptococcus mutans.</a> FEMS Microbiology Letters. 363 (11), 101 (2016).</li><li>Murata, T., Okada, A., Matin, K., Hanada, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generation+of+a+gene-disrupted+Streptococcus+mutans+strain+without+gene+cloning.">Generation of a gene-disrupted Streptococcus mutans strain without gene cloning.</a> Journal of Visualized Experiments. (128), (2017).</li><li>Hanada, N., Kuramitsu, H. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+characterization+of+the+Streptococcus+mutansgtfC+gene,+coding+for+synthesis+of+both+soluble+and+insoluble+glucans.">Isolation and characterization of the Streptococcus mutansgtfC gene, coding for synthesis of both soluble and insoluble glucans.</a> Infection and Immunity. 56 (8), 1999-2005 (1988).</li><li>LeBlanc, D. J., Lee, L. N., Inamine, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cloning+and+nucleotide+base+sequence+analysis+of+a+spectinomycin+adenyltransferase+AAD(9)+determinant+from+Enterococcus+faecalis.">Cloning and nucleotide base sequence analysis of a spectinomycin adenyltransferase AAD(9) determinant from Enterococcus faecalis.</a> Antimicrobial Agents and Chemotherapy. 35 (9), 1804-1810 (1991).</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> Journal of Visualized Experiments. (63), e3998 (2012).</li><li>Database, J. S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PCR:+The+Polymerase+Chain+Reaction.">PCR: The Polymerase Chain Reaction.</a> Journal of Visualized Experiments. , (2019).</li><li>Database, J. S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DNA+Gel+Electrophoresis.">DNA Gel Electrophoresis.</a> Journal of Visualized Experiments. , (2019).</li><li>Database, J. S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gel+Purification.">Gel Purification.</a> Journal of Visualized Experiments. , (2019).</li><li>Wingfield, P. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+precipitation+using+ammonium+sulfate.">Protein precipitation using ammonium sulfate.</a> Current Protocols in Protein Science. 84 (1), (2016).</li><li>Database, J. S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Separating+Protein+with+SDS-PAGE.">Separating Protein with SDS-PAGE.</a> Journal of Visualized Experiments. , (2019).</li><li>Database, J. S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Western+Blot.">The Western Blot.</a> Journal of Visualized Experiments. , (2019).</li><li>Smith, 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=Measurement+of+protein+using+bicinchoninic+acid.">Measurement of protein using bicinchoninic acid.</a> Analytical Biochemistry. 150 (1), 76-85 (1985).</li><li>Perry, D., Wondrack, L. M., Kuramitsu, H. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+transformation+of+putative+cariogenic+properties+in+Streptococcus+mutans.">Genetic transformation of putative cariogenic properties in Streptococcus mutans.</a> Infection and Immunology. 41 (2), 722-727 (1983).</li><li>Lau, P. C., Sung, C. K., Lee, J. H., Morrison, D. A., Cvitkovitch, D. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PCR+ligation+mutagenesis+in+transformable+streptococci:+application+and+efficiency.">PCR ligation mutagenesis in transformable streptococci: application and efficiency.</a> Journal of Microbiological Methods. 49 (2), 193-205 (2002).</li><li>Ge, X., Xu, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genome-wide+gene+deletions+in+Streptococcus+sanguinis+by+high+throughput+PCR.">Genome-wide gene deletions in Streptococcus sanguinis by high throughput PCR.</a> Journal of Visualized Experiments. (69), (2012).</li></ol>

The design of primers is the most critical step in the protocol. The sequences of the gtfC-reverse and spcr-forward primers were automatically determined based on the sequences of both the 3&#8242; end region of gtfC and the 5&#8242; end region of spcr. Each primer includes 24 complementary bases that encode a GS linker and a His-tag-coding sequence at their 5&#39; regions. Disruption of the native regulatory sequences located in the upstream flanking regions can ...

Analysis of a gene&#39;s function usually involves comparison of phenotypic traits of wild-type strains to strains in which the gene of interest has been disrupted.Once the gene-disrupted strain is produced, exogenous addition of the gene product allows functional restoration.
The most common method for obtaining purified gene products required for subsequent restoration assays is by performing heterologous expression in Escherichia coli1. However, the expression of membrane proteins or high molecular mass proteins is often difficult using this system1. In these cases, the target protein is usually isolated from the cells that natively synthesizes the protein through a complex series of steps, which may lead to loss of the gene product. To overcome these issues, a simple procedure has been developed for gene product purification following a gene disruption method2, PCR-based DNA splicing method3&#160;(designated two-step fusion PCR), and electroporation for genetic transformation in Streptococcus mutans. Addition of a polyhistidine tag (His-tag) to the C-terminus of the gene product facilitates its purification by immobilized metal affinity chromatography (IMAC).
To isolate the His-tag-expressing strain, the entire genomic DNA of the gene of interest (in this His-tag-expressing gene-disrupted strain) is replaced with an antibiotic-resistant marker gene. The procedure for generating the His-tag-expressing strainis nearly identical to that for generating a gene-disrupted strain as described previously4,5. Therefore, the methods for gene disruption and gene product isolation should be performed as serial experiments for the functional analysis.
In the present work, a polyhistidine-coding sequence is attached to the 3&#8242; end of the gtfC (GenBank locus tag SMU_1005) gene, encoding glucosyltransferase-SI (GTF-SI) in S. mutans6. Then, expression studies in a streptococcal species were performed. Achieving heterologous gtfC expression by E. coli is difficult, likely because of the high molecular mass of GTF-SI. This strain is named S. mutans His-gtfC. A schematic illustration depicting the organization of the gtfC and spectinomycin resistance gene cassette (spcr)7 loci in wild-type S. mutans (S. mutans WT) and its derivatives is shown in Figure 1. The GTF-SI is a secretory protein that contributes to the development of cariogenic dental biofilm6. Under the presence of sucrose, an adherent biofilm is observed on a smooth glass surface in WT S. mutans strain but not in the S. mutans gtfC-disrupted strain (S. mutans &#916;gtfC)2,5. Biofilm formation is restored in S. mutans &#916;gtfC upon exogenous addition of the recombinant GTF-SI. The strain, S. mutans His-gtfC, is then used to produce the recombinant GTF-SI.

<table>
	<tbody>
		<tr>
			<td>Agarose</td>
			<td>Nippon Genetics</td>
			<td>NE-AG02</td>
			<td>For agarose gel electrophoresis</td>
		</tr>
		<tr>
			<td>Anaeropack</td>
			<td>Mitsubishi Gas Chemical</td>
			<td>A-03</td>
			<td>Anaerobic culture system</td>
		</tr>
		<tr>
			<td>Anti-His-Tag monoclonal antibody</td>
			<td>MBL</td>
			<td>D291-7</td>
			<td>HRP-conjugated</td>
		</tr>
		<tr>
			<td>BCA protein assay kit</td>
			<td>Thermo Fisher Scientific</td>
			<td>23227</td>
			<td>Measurement of protein concentration</td>
		</tr>
		<tr>
			<td>Brain heart infusion broth</td>
			<td>Becton, Dickinson</td>
			<td>237500</td>
			<td>Bacterial culture medium</td>
		</tr>
		<tr>
			<td>CBB R-250</td>
			<td>Wako</td>
			<td>031-17922</td>
			<td>For biofilm staining</td>
		</tr>
		<tr>
			<td>Centrifugal ultrafiltration unit</td>
			<td>Sartorius</td>
			<td>VS2032</td>
			<td>Buffer replacement and protein concentration</td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Kubota</td>
			<td>7780II</td>
			<td></td>
		</tr>
		<tr>
			<td>Chromatographic column</td>
			<td>Bio-Rad</td>
			<td>7321010</td>
			<td>For IMAC</td>
		</tr>
		<tr>
			<td>Dialysis membrane clamp</td>
			<td>Fisher brand</td>
			<td>21-153-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Dialysis tubing</td>
			<td>As One</td>
			<td>2-316-06</td>
			<td></td>
		</tr>
		<tr>
			<td>DNA polymerase</td>
			<td>Takara</td>
			<td>R045A</td>
			<td>High-fidelity DNA polymerase</td>
		</tr>
		<tr>
			<td>DNA sequencing</td>
			<td>Eurofins Genomics</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ECL substrate</td>
			<td>Bio-Rad</td>
			<td>170-5060</td>
			<td>For western blotting</td>
		</tr>
		<tr>
			<td>EDTA (0.5 M pH 8.0)</td>
			<td>Wako</td>
			<td>311-90075</td>
			<td>Tris-EDTA buffer preparation</td>
		</tr>
		<tr>
			<td>Electroporation cuvette</td>
			<td>Bio-Rad</td>
			<td>1652086</td>
			<td>0.2 cm gap</td>
		</tr>
		<tr>
			<td>Electroporator</td>
			<td>Bio-Rad</td>
			<td>1652100</td>
			<td></td>
		</tr>
		<tr>
			<td>EtBr solution</td>
			<td>Nippon Gene</td>
			<td>315-90051</td>
			<td>For agarose gel electrophoresis</td>
		</tr>
		<tr>
			<td>Gel band cutter</td>
			<td>Nippon Genetics</td>
			<td>FG-830</td>
			<td></td>
		</tr>
		<tr>
			<td>Gel extraction kit</td>
			<td>Nippon Genetics</td>
			<td>FG-91202</td>
			<td>DNA extraction from agarose gel</td>
		</tr>
		<tr>
			<td>Imager</td>
			<td>GE Healthcare</td>
			<td>29083461</td>
			<td>For SDS-PAGE and western blotting</td>
		</tr>
		<tr>
			<td>Imidazole</td>
			<td>Wako</td>
			<td>095-00015</td>
			<td>Binding buffer and elution buffer preparation</td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>Nippon Medical &#38; Chemical Instruments</td>
			<td>EZ-022</td>
			<td>Temperature setting: 4 &#176;C</td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>Nippon Medical &#38; Chemical Instruments</td>
			<td>LH-100-RDS</td>
			<td>Temperature setting: 37 &#176;C</td>
		</tr>
		<tr>
			<td>Membrane filter</td>
			<td>Merck Millipore</td>
			<td>JGWP04700</td>
			<td>0.2 &#181;m diameter</td>
		</tr>
		<tr>
			<td>Microcentrifuge</td>
			<td>Kubota</td>
			<td>3740</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Wako</td>
			<td>191-01665</td>
			<td>Preparation of binding buffer and elution buffer</td>
		</tr>
		<tr>
			<td>NaH2PO4&#183;2H2O</td>
			<td>Wako</td>
			<td>192-02815</td>
			<td>Preparation of binding buffer and elution buffer</td>
		</tr>
		<tr>
			<td>NaOH</td>
			<td>Wako</td>
			<td>198-13765</td>
			<td>Preparation of binding buffer and elution buffer</td>
		</tr>
		<tr>
			<td>(NH4)2SO4</td>
			<td>Wako</td>
			<td>015-06737</td>
			<td>Ammonium sulfate precipitation</td>
		</tr>
		<tr>
			<td>Ni-charged resin</td>
			<td>Bio-Rad</td>
			<td>1560133</td>
			<td>For IMAC</td>
		</tr>
		<tr>
			<td>PCR primers</td>
			<td>Eurofins Genomics</td>
			<td>Custom-ordered</td>
			<td></td>
		</tr>
		<tr>
			<td>Protein standard</td>
			<td>Bio-Rad</td>
			<td>161-0381</td>
			<td>For SDS-PAGE and western blotting</td>
		</tr>
		<tr>
			<td>Solvent filtration apparatus</td>
			<td>As One</td>
			<td>FH-1G</td>
			<td></td>
		</tr>
		<tr>
			<td>Spectinomycin</td>
			<td>Wako</td>
			<td>195-11531</td>
			<td>Antibiotics; use at 100 &#956;g/mL</td>
		</tr>
		<tr>
			<td>Sterile syringe filter</td>
			<td>Merckmillipore</td>
			<td>SLGV004SL</td>
			<td>0.22 &#181;m diameter</td>
		</tr>
		<tr>
			<td>Streptococus mutans &#916;gtfC</td>
			<td>Stock strain in the lab.</td>
			<td></td>
			<td>gtfC replaced with spcr</td>
		</tr>
		<tr>
			<td>Streptococus mutans UA159</td>
			<td>Stock strain in the lab.</td>
			<td></td>
			<td>S. mutans ATCC 700610, Wild-type strain</td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Wako</td>
			<td>196-00015</td>
			<td>For biofilm development</td>
		</tr>
		<tr>
			<td>TAE (50 &#215; )</td>
			<td>Nippon Gene</td>
			<td>313-90035</td>
			<td>For agarose gel electrophoresis</td>
		</tr>
		<tr>
			<td>Thermal cycler</td>
			<td>Bio-Rad</td>
			<td>PTC-200</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris-HCl (1 M, pH 8.0)</td>
			<td>Wako</td>
			<td>314-90065</td>
			<td>Tris-EDTA buffer preparation</td>
		</tr>
	</tbody>
</table>

purification of a high molecular mass protein in streptococcus mutans

Elucidation of a gene&#39;s function typically involves comparison of phenotypic traits of wild-type strains and strains in which the gene of interest has been disrupted. Loss of function following gene disruption is subsequently restored by exogenous addition of the product of the disrupted gene. This helps to determine the function of the gene. A method previously described involves generating a gtfC gene-disrupted Streptococcus mutans strain. Here, an undemanding method is described for purifying the gtfC gene product from the newly generated S. mutans strain following the gene disruption. It involves the addition of a polyhistidine-coding sequence at the 3&#8242; end of the gene of interest, which allows simple purification of the gene product using immobilized metal affinity chromatography. No enzymatic reactions other than PCR are required for the genetic modification in this method. The restoration of the gene product by exogenous addition after gene disruption is an efficient method for determining gene function, which may also be adapted to different species.

Figure 3 shows the size of each amplicon from the first PCR (Figure 3A) and second PCR (Figure 3B). The size of each amplicon corresponded with the predicted size, as described in Table 1. Figure 4A shows S. mutans colonies transformed with the second PCR product and plated on the BHI agar plates containing spectinomycin. Colony PCR products wer...

Watch this Scientific Journal Video about Purification of a High Molecular Mass Protein in Streptococcus mutans at JoVE.com

Purification of a High Molecular Mass Protein in Streptococcus mutans

Described here is a simple method for the purification of a gene product in Streptococcus mutans. This technique may be advantageous in the purification of proteins, especially membrane proteins and high molecular mass proteins, and can be used with various other bacterial species.

Purification of a High Molecular Mass Protein in Streptococcus mutans

Elucidation of a gene&#39;s function typically involves comparison of phenotypic traits of wild-type strains and strains in which the gene of interest has ...

This method can help answer key questions in the microbiology field such as, how a gene product that is difficult to express in E.Coli purifies. The main advantages of this technique are that no enzymatic reaction, other than PCR, is the carrier, and common applications for protein purification can be used. Though this method can provide insight into protein purification in streptococcus mutans, it can also be a apprised to other microbiota species.Demonstrating the procedure will be Dr.Mamiko Yamashita, a grad student from our laboratory. After primer design and genomic DNA extraction from streptococcus mutans, perform the first PCR using the wild-type streptococcus mutans and GFC disrupted streptococcus mutans genome as the PCR templates. Amplify the regions harboring the downstream part of the gtfC gene and those harboring the spectinomycin resistance gene using the prepared gtfC-forward and reverse primer and spc r-forward and reverse primer.Then, electrophorese each PCR product on 1%agarose gel. Use a gel bandcutter to excise the desired DNA fragments of approximately 1, 000 base pairs and 2, 000 base pairs from the gel into microcentrifuge tubes. Add 500 microliters of solubilizing buffer into each tube and incubate them for 10 minutes at 56 degrees Celsius to dissolve the gel slices.Purify the fragments using silica membrane-based gel extraction method. Perform a second PCR using the products of the first PCR as PCR templates with the nested-forward and nested-reverse primers. When the second PCR product cannot be confirmed by electrophoresis, another nested primer's pair should be designed.electrophorese five microliters of the PCR mixture on the agarose gel. Confirm the generation of the appropriate amplicon of approximately 3, 000 base pairs by ethidium bromide gel staining image and proceed according to the manuscript. Now, mix five microliters of the concentrated second PCR product to the 50-microliter aloquot of ice-cold, competent wild-type streptococcus mutan cells, frozen previously.Add the mixture into an electroporation cuvette and place the cuvette into the cuvette chamber of the electroporation apparatus. Give a single electric pulse of 1.8 kilovolts, 600 ohms, and 10 microfarads for 2.5 milliseconds to the cells. Add 500 microliters of brain-heart infusion broth into the cuvette.Immediately spread 10 to 100 microliters of the suspension onto brain-heart infusion auger plates containing spectinomycin. Incubate the plates for two to six days at 37 degrees Celsius until colonies have grown sufficiently to be picked up. After generation of streptococcus mutans polyhistidine coding sequence incorporated strain and overnight inoculation without spectinomycin according to the manuscript, centrifuge the bacterial culture suspension for 20 minutes at 10, 000 times g at four degrees Celsius.Transfer the culture supernatant into a three-liter glass beaker. To concentrate the proteins from the culture supernatant, place the two-liter supernatant on a magnetic stirrer and start vigorous stirring. Add 1, 122 grams of ammonium sulfate and allow the precipitate to form with vigorous stirring at four degrees Celsius over a four-hour period or overnight.Next.centrifuge the ammonium sulfate precipitated solution at 15, 000 times g for 20 minutes at four degrees Celsius. Decant the supernatant. With a spatula, collect the precipitate and transfer it into a 200-milliliter glass beaker.Resuspend the pellets in 35 milliliters of binding buffer. Then, transfer each approximately 25 milliliters of the suspension into a regenerated cellulose dialysis tubing. Place the dialysis tubing into 2.5 liters of the stirring binding buffer on a stirrer at four degrees Celsius to dialyze the suspension.Replace the dialysis solution after two hours and continue dialysis overnight. Next transfer the dialyzed suspension from the tubing to centrifuge tubes and place the tubes in the centrifuge at 20, 000 times g for 10 minutes at four degrees Celsius. With section filtration equipment, pour the supernatant over a 0.2-micrometer membrane filter to filter.Transfer the filtrate to a 75-milliliter flask. To fractionate the polyhistidine-tagged gtfSI from the filtrated suspension, first prepare an immobilized metal affinity chromatography. After equilibrating the resin according to the manuscript, close the Hoffman pinch cock.Add five milliliters of the filtered suspension into the column to make a slurry. Then, transfer all the slurry to the remaining filtered suspension and swirl the mixture gently for 30 minutes at four degrees Celsius. Load the mixture back into the column.Open the Hoffman pinch cock to remove the suspension by the gravity flow. Wash the IMAC resin with 20 milliliters of binding buffer and then, elute 20 milliliters of elution buffer to obtain the recombinant gtfSI. After that, load the eluate into a centrifugal ultra filtration tube and centrifuge the solution at 2, 000 times g for one to five minutes to concentrate the solution.Empty the filtrate container and add 15 milliliters of storage buffer into the tube. Centrifuge the sample again and repeat the process two additional times. The recombinant gtfSI solution is finally concentrated to approximately one milliliter.Transfer the concentrate into a microcentrifuge tube and store at four degrees Celsius. Continue with the rest functional restoration protocol. In this protocol, the agarose gel electrophoresis shows that the size of each amplicon from the first PCR and the second PCR corresponded with the predicted size.Streptococcus mutans colonies were transformed with the second PCR product and plated on the brain-heart infusion auger plates containing spectinomycin. Colony PCR products run on the agarose gel shows that each amplicon was of the predicted size. Protein purified with immobilized metal affinity chromatography was observed as a single band by SDS-PAGE.Western blot, performed using the anti-polyhistidine antibody, confirmed that the observed band was the expected polyhistidine-tagged protein of 160 kilodaltons. The sucrose-derived biofilm forming ability was only seen with streptococcus mutans wild-type and streptococcus mutans His-gtfC, which formed an adherent biofilm on the tube wall in the presence of 1%sucrose. This was not observed in streptococcus mutans delta gtfC.However, the addition of 25 micrograms of the recombinant gtfSI restored the adherent biofilm formation ability in streptococcus mutans delta gtfC. Since the success of this method depends on the second PCR amplification, the second PCR product must be confirmed by electrophoresis. Already, histidine-type protein obtained by this method is also convening to functional acids, such as protein-protein interactions.After its development, this technique, in combination with gene disruption, paved the way for researchers in the field of microbiology to explore gene function.

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JoVE Journal

Immunology and Infection

5.7K vistas.  Tsurumi University School of Dental Medicine. Este método puede ayudar a responder preguntas clave en el campo de la microbiología, tales como, cómo un producto genético que es difícil de expresar en E. coli purifica. Las principales ventajas de esta técnica son que ninguna reacción enzimática, aparte de la PCR, es el portador, y se pueden utilizar aplicaciones comunes para la purificación de proteínas. Aunque este método puede proporcionar información sobre la purificación de proteínas en estreptococos mutanos, también pu...