Dear all, I'm looking at a crystal structure (1H4G) where the N-terminal Glu residue has cyclized to pyroglutamic acid (PCA). The protein was expressed in and secreted from bacteria (*Bacillus licheniformis*), and the crystallization conditions for 3 ul hanging drops were 2 ul protein solution (10 mg/ml in 100 mM sodium acetate pH 6.0) + 1 ul reservoir solution (100 mM MES pH 6.5, 30% ammonium sulphate).
As I wouldn't typically expect this kind of post-translational modification to appear in bacteria (please correct me if I'm mistaken about this), I suspect the presence of PCA here to be an artifact of crystallization. Have others seen cyclization of N-terminal Glu or Gln to PCA under such acidic crystallization conditions? I'd be interested in seeing any relevant literature you might be able to suggest. Many thanks, Jared ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
