Team:INSA-Lyon/molecular

From 2014.igem.org

Revision as of 14:18, 11 October 2014 by Tcyr (Talk | contribs)

Curly'on - IGEM 2014 INSA-LYON

IGEM

MOLECULAR MODELISATION

One of the main goals of our modeling work this year was to understand the structure of the curlin subunit protein, CsgA and it's behavior when engineered with a tag constituted of either six histidines (that we will call His1-tag from now on) or twice that motif (His2-tag), since such a peptide is known for its nickel chelation properties. We then discussed over our results with the wetlab members to define a way to confirm the accuracy of our model, and so we were able to assess that, in accordance with litterature, the best position for the tag was by the C-terminus of the protein. We also determined that the His-tag was likely to take floating conformation instead of folding itself around CsgA.

Methods

For a numerical molecular model, what is needed before anything else is the program that will be used. As far as we were concerned, we chose to use Sybyl-X, which we began to use this year, and offers a number of tools as well as powerful calculation algorithm. Then we had to find a file containing the structure of CsgA. Indeed, reproducing it from scratch only from its amino acid sequence would be close to impossible since what the program allows us to do is only theoretical, it cannot know the right conformation of a complex protein just like that. Thus you have to whether build the protein yourself, by specifying the sequence, angles and distances between amino acids, which will almost certainly result in failure for a protein as complex as CsgA; or you can provide the program with a pdb file, which is a file that gives the spatial coordinates of every atom in the molecule. However, curli are extremely stable and hard to characterize and we weren't able to find any such file in the banks we searched, be it the protein data bank, uniprot, and many others. We managed to get a pdb file of the CsgA protein only thanks to the generosity of professor M. Chapman from the University of Michigan who sent us his work and to whom we are really grateful.image CsgA To work on the protein, we mainly used two functions of Sybyl-X :
  1. the minimize option, that search ;
  2. we developped both a mathematical model describing the polymerisation of CsgA, and a simulation program of the same phenomenon ; our aim was for those two models to serve as a basis for future teams working with curli.
From there it is really easy to add a short polypeptids sequence to the protein

CsgA Engineering

Retrieved from "http://2014.igem.org/Team:INSA-Lyon/molecular"