Modifying the protein to crystallize better: Difference between revisions

There is a webserver, called SER (Surface Entropy Reduction Prediction Server), which aims to predict sites that are most suitable for mutation designed to enhance crystallizability:

http://nihserver.mbi.ucla.edu/SER/

== [[Chemical Modification]]==

Another method for enhancing the crystallizability of proteins involves chemical modification of specific sidechains.

Several methods are available:

1. Modification of lysine residues

This method, pioneered by the Rayment laboratory, involves the methylation -- under reducing conditions -- of lysine residues. This increases the hydrophobicity of the modified lysine sidechains, reduces the overall solubility of the protein, and -- for some proteins -- promotes the formation of ordered crystal contacts.  

A recent study (Walter et al. [2006] "Lysine Methylation as a Routine Rescue Strategy for Protein Crystallization" Structure 14:1617–1622) demonstrated that, out of 10 non-crystallizable proteins,  

4 proteins became crystallisable after reductive methylation.

2. Modification of cyteine residues  

This method involves the carboxymethylation -- under reducing conditions -- of single cysteine residues. This effectively neutralizes the cysteine residues (some of which are chemically reactive), increase the overall solubility of proteins and can help prevent aggregation and denaturation problems of proteins.

References:

Eiler S et al. (2001) Protein Expr Purif. 22(2):165-73

http://www.ionsource.com/Card/cmc/method.htm  -- A protocol for carbocymethylation