[Protein-analysis] Bizzare Posttranslational modification during E. coli overexpression

nomadiq via proteins%40net.bio.net (by nomadiq from gmail.com)
Fri Jun 29 13:35:01 EST 2007


Im pretty sure a protein I am overexpressing from a pET15B vector has
a bizzare posttranslational modification. Mass spec has identified the
added mass as 958 Da (to about 20% of the protein molecules). Im
overexpressing in BL21 Lambda DE3 and my protein is cleaved away from
the His tag with thrombin.

Anyone have any ideas what kind of modification would add 958 Da? I
have checked and it doesn't seem the mass can be explained by added
amino acids.

Thanx in advance,


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