Name: assessing two-dimensional crystallization trials of small membrane proteins for structural biology studies by electron crystallography
Uploaded: 2010-10-29T17:00:00
Description: Watch this Scientific Journal Video about Assessing Two-dimensional Crystallization Trials of Small Membrane Proteins for Structural Biology Studies by Electron Crystallography at JoVE.com

We thank our collaborators for providing valuable protein samples, which contributed to some of our methods related experience and observations. G&uuml;nther Schmalzing kindly provided the opportunity to FR to join this project. Barbara Armbruster, Jacob Brink and Deryck Mills are thanked for their outstanding help and input on equipment. Funding was provided by NIH grant HL090630.

1. Grid Preparation of 2D Crystallization Trials
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<li>	Carbon-coated 400-mesh copper EM grids are prepared by negative stain. Uranyl acetate is frequently used and provides a long-lasting stain in terms of storage of the solution for several months before use as well as suitability for long-term storage of grids. In contrast, other negative stains such as uranyl formate, while providing excellent staining, need to be freshly made 1. For fast preparation of a large number of grids to be used for scre...

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	<li>Johansen, B. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bright+field+electron+microscopy+of+biological+specimens+V.+A+low+dose+pre-irradiation+procedure+reducing+beam+damage.">Bright field electron microscopy of biological specimens V. A low dose pre-irradiation procedure reducing beam damage.</a> Micron. 7, 145-156 (1976).</li><li>Schmidt-Krey, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electron+crystallography+of+membrane+proteins:+Two-dimensional+crystallization+and+screening+by+electron+microscopy.">Electron crystallography of membrane proteins: Two-dimensional crystallization and screening by electron microscopy.</a> Methods. 41, 417-426 (2007).</li><li>Wang, D. N., K&#252;hlbrandt, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-resolution+electron+crystallography+of+light-harvesting+chlorophyll+a/b-protein+complex+in+three+different+media.">High-resolution electron crystallography of light-harvesting chlorophyll a/b-protein complex in three different media.</a> J Mol Biol. 217, 691-699 (1991).</li><li>Schmidt-Krey, I., Rubinstein, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electron+cryomicroscopy+of+membrane+proteins:+specimen+preparation+for+two-dimensional+crystals+and+single+particles.">Electron cryomicroscopy of membrane proteins: specimen preparation for two-dimensional crystals and single particles.</a> Micron. , (2010).</li><li>Schmidt-Krey, I., Mutucumarana, V., Haase, W., Stafford, D. W., K&#252;hlbrandt, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-dimensional+crystallization+of+human+vitamin+K-dependent+&amp;gamma;-glutamyl+carboxylase.">Two-dimensional crystallization of human vitamin K-dependent &amp;gamma;-glutamyl carboxylase.</a> J Struct Biol. 157, 437-442 (2007).</li><li>Trachtenberg, S., DeRosier, D. J., Zemlin, F., Beckmann, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-helical+perturbations+of+the+flagellar+filament:+Salmonella+typhimurium+SJW117+at+9.6+&amp;Aring;+resolution.">Non-helical perturbations of the flagellar filament: Salmonella typhimurium SJW117 at 9.6 &amp;Aring; resolution.</a> J Mol Biol. 276, 759-773 (1998).</li><li>Zhao, G., Johnson, M. C., Schnell, J. R., Kanaoka, Y., Irikura, D., Lam, B. K., Austen, K. F., Schmidt-Krey, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-dimensional+crystallization+conditions+of+human+leukotriene+C4+synthase+requiring+a+particularly+large+combination+of+specific+parameters.">Two-dimensional crystallization conditions of human leukotriene C4 synthase requiring a particularly large combination of specific parameters.</a> J Struct Biol. 169, 450-454 (2010).</li><li>Cheng, A., Leung, A., Fellmann, D., Quispe, J., Suloway, C., Pulokas, J., Abeyrathne, P. D., Lam, J. S., Carragher, B., Potter, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Towards+automated+screening+of+two-dimensional+crystals.">Towards automated screening of two-dimensional crystals.</a> J Struct Biol. 160, 324-331 (2007).</li><li>Vink, M., Derr, K. D., Love, J., Stokes, D. L., Ubarretxena-Belandia, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+high-throughput+strategy+to+screen+2D+crystallization+trials+of+membrane+proteins.">A high-throughput strategy to screen 2D crystallization trials of membrane proteins.</a> J Struct Biol. 160, 295-304 (2007).</li></ol>

Proper evaluation of samples requires careful assessment of a sufficient number of membranes. For example, samples with as low as 2% crystalline arrays out of over 180 imaged proteoliposomes gave critical information for quick optimization of 2D crystallization conditions 7.
When precipitation of the protein occurs, a grid might be abandoned from further screening after inspection at low magnification, although occasional partial precipitation of protein occurs. Even very small m...

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		<th>Material Name</th>
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<td>400-mesh copper TEM grids coated with carbon film</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>forceps: regular and anti-capillary </td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>Dumont #5 and Dumont N5AC or similar</td>
</tr>
<tr>
<td>Micropipette and pipette tips</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>Whatman #4 filter paper</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<tr>
<td>1% uranyl acetate</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
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<td>Dialysis sample to be screened for 2D crystals</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
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<td>Glycerol/sucrose-free dialysis buffer</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>Optional</td>
</tr>
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<td>JEOL-1400 transmission electron microscope (TEM)</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>similar 80 &#x2013; 120kV TEM equipped with an Lab6 or tungsten filament and film and/or CCD cameras (Gatan Orius SC1000 and/or UltraScan1000 CCD cameras and Gatan Digitial Micrograph software package or Tietz cameras (TVIPS)) </td>
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assessing two-dimensional crystallization trials of small membrane proteins for structural biology studies by electron crystallography

Electron crystallography has evolved as a method that can be used either alternatively or in combination with three-dimensional crystallization and X-ray crystallography to study structure-function questions of membrane proteins, as well as soluble proteins. Screening for two-dimensional (2D) crystals by transmission electron microscopy (EM) is the critical step in finding, optimizing, and selecting samples for high-resolution data collection by cryo-EM. Here we describe the fundamental steps in identifying both large and ordered, as well as small 2D arrays, that can potentially supply critical information for optimization of crystallization conditions.
By working with different magnifications at the EM, data on a range of critical parameters is obtained. Lower magnification supplies valuable data on the morphology and membrane size. At higher magnifications, possible order and 2D crystal dimensions are determined. In this context, it is described how CCD cameras and online-Fourier Transforms are used at higher magnifications to assess proteoliposomes for order and size.
While 2D crystals of membrane proteins are most commonly grown by reconstitution by dialysis, the screening technique is equally applicable for crystals produced with the help of monolayers, native 2D crystals, and ordered arrays of soluble proteins. In addition, the methods described here are applicable to the screening for 2D crystals of even smaller as well as larger membrane proteins, where smaller proteins require the same amount of care in identification as our examples and the lattice of larger proteins might be more easily identifiable at earlier stages of the screening.

Watch this Scientific Journal Video about Assessing Two-dimensional Crystallization Trials of Small Membrane Proteins for Structural Biology Studies by Electron Crystallography at JoVE.com

Assessing Two-dimensional Crystallization Trials of Small Membrane Proteins for Structural Biology Studies by Electron Crystallography

Evaluating two-dimensional (2D) crystallization trials for the formation of ordered membrane protein arrays is a highly critical and difficult task in electron crystallography. Here we describe our approach in screening for and identifying 2D crystals of predominantly small membrane proteins in the range of 15 &#x2013; 90kDa.

Electron crystallography has evolved as a method that can be used either alternatively or in combination with three-dimensional crystallization and X-ray ...

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