Hi, Unless you've already tried exhaustively - why not to try MIR, as you mentioned - there are many derivatives out there to be tried and with a small protein the chances are pretty good. All you need is one good derivative :)
This certainly sounds easier than mutating exposed Met! Cross-seeding with S-Met crystals into Se-Met protein worked for me on several occasions. Artem -----Original Message----- From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On Behalf Of Joe Smith Sent: Tuesday, May 27, 2008 5:11 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Problem with crystallization of Se-Met labeled protein Dear all, Sorry for an off-topic query. I have been unable to crystallize a Se-met containing protein (8 Met in 206 amino acids) in the native crystallization condition ( 0.1 M Tris pH 8.5, 1.2 M K-Na-tartrate; Theoretical pI of protein is 8.4). As expected, solubility of Se-Met containing protein is little less than the wild type. Other than seeding, i don't know what else I should try for obtaining a Se-met crystal for phasing. Can I mutate some of the exposed Met (based on secondary structure prediction and homologous structure) to Ala as I feel I don't really need 8 Se for phasing 208 aa long polypeptide. I want to know what generally one should do when Se-Met containing proteins fail to crystallize. Thanks in advance. Joe PS: Since, protein contains 3 Cys residues.. I am also planning to try my luck with heavy atom compounds containing Hg.
