Hi, Yes, this does happen. Spontaneous α-N-6-Phosphogluconoylation of a "His Tag" inEscherichia coli:The Cause of Extra Mass of 258 or 178 Da in Fusion Proteins
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6W9V-45N4K22-R&_us er=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1& _urlVersion=0&_userid=10&md5=453fd46805ef7137c62705a5ae80384e There are other options out there too but this one comes to mind first. Artem -----Original Message----- From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of Torres-Larios Alfredo Sent: Monday, January 19, 2009 8:26 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Posttranslational modifications of recombinant proteins expressed in E. coli? Dear all, I know this sounds weird (and besides, it's a non CCP4 question), but does anyone know any reports or has worked with a recombinant protein that is apparently post translationally modified by E. coli? We have an enzyme with two populations that have been sequenced at the N-terminus. Both have the same sequence at that region, but by mass spec the MW of one population (1) is 200 Da more than expected. The other population (2) has the "correct" MW. The enzyme (1) has 10% activity with respect to (2). The C-terminal is far away from the active site. Another funny thing is that the ratio of the two populations changes from batch to batch, and the heterogeneity arises before cleaving the N-terminal His tag with TEV protease. Any comments will be greatly acknowledged. Thanks a lot in advance, Alfredo. Alfredo Torres-Larios, PhD Assistant Professor Instituto de Fisiologia Celular, UNAM Circuito Exterior S/N. Ciudad Universitaria Mexico, DF, Mexico ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.
