Dear Umar,
It's probably not local flexibility or the interaction with other molecules, such as DNA, that prevents your protein from crystallising but an unfavourable enthalpy/entropy balance of long side chains which are potentially restricted by forming crystal contacts. Mutation of these to small, low-entropy residues such as alanine might help. Have a look at the "surface entropy reduction prediction server" for example (http://nihserver.mbi.ucla.edu/SER/intro.php) and see if this could be helpful in your case. Cheers and good luck, Uli Gohlke --------------------------------------------------------------------------- dr ulrich gohlke staff scientist - macromolecular structure and interaction max-delbrück-centre for molecular medicine (mdc) +49 30 9406 - 2725 (w) +49 30 9406 - 2548 (fax) ulrich.goh...@mdc-berlin.de http://www.mdc-berlin.de/en/research/research_teams/macromolecular_structure_and_interaction/ From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of Jan Rash Sent: Monday, November 02, 2009 2:40 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Crystallization of lysine and arginine rich proteins Dear All, I have a question regarding the crystallization of lysine and arginine rich protein around 13%. So far our attempts to crystallize this protein have not been successful although the secondary structure predictions, CD spectroscopy measurements clearly show that this protein is folded. I presume that these lysine and arginine are the sources of the local flexibility in the protein even though the protein is globular overall. Moreover, my attempts to crystallize the limited proteolysis fragments also did not achieve crystals. I have also tried the crystallization with its binding partners and could not succeed. I think any compound that binds to the lysine/arginine side chains might affect the crystallization process thereby reducing the internal flexibility of protein. Can anybody suggest some effective strategy for the crystallization? Thanks Umar
