Thanks for the suggestions/ideas. The protein is recombinantly expressed in E.coli. It does in fact show a metal dependency. We mass spec'd the peaks once looking for phosphorylation, which was not detected, but we only got about 60-70% sequence coverage so it was not very helpful.
Quoting "Nadir T. Mrabet" <nadir.mra...@medecine.uhp-nancy.fr>: > Given no info on the protein, it can be anything. > Is it recombinant? Which host? etc. > > Oxydation (cys, met) is also a possibility > By the way, deamination concerns asn and gln, not lys. > > Best, > > Nadir > > Pr. Nadir T. Mrabet > Structural& Molecular Biochemistry > Nutrigenex - INSERM U-954 > Nancy University, School of Medicine > 9, Avenue de la Foret de Haye, BP 184 > 54505 Vandoeuvre-les-Nancy Cedex > France > Phone: +33 (0)3.83.68.32.73 > Fax: +33 (0)3.83.68.32.79 > E-mail: Nadir.Mrabet<at> medecine.uhp-nancy.fr > > > > On 18/02/2011 19:45, Soisson, Stephen M wrote: >> Possibly deamidation of the protein, in particluar one or more >> lysines. What does the Mass spec look like? >> Cheers, >> Steve >> >> ------------------------------------------------------------------------ >> *From:* CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] *On >> Behalf Of *Ulli Hain >> *Sent:* Friday, February 18, 2011 12:14 PM >> *To:* CCP4BB@JISCMAIL.AC.UK >> *Subject:* [ccp4bb] off-topic: 2 peaks on Cation >> >> Hi, I was wondering if anyone had possible explanations for a >> recombinantly expressed soluble protein that runs as 2 equal, >> slightly overlapping peaks on a cation exhanger but as one peak on a >> size exclusion column and same electrophoretic mobility on SDS-PAGE. >> -Ulli >> >> >> Adelaide Ulricke Hain >> PhD Candidate >> Johns Hopkins Bloomberg School of Public Health >> Department of Biochemistry and Molecular Biology >> 615 North Wolfe Street >> Baltimore, MD 21205 >> Notice: This e-mail message, together with any attachments, contains >> information of Merck& Co., Inc. (One Merck Drive, Whitehouse Station, >> New Jersey, USA 08889), and/or its affiliates Direct contact information >> for affiliates is available at >> http://www.merck.com/contact/contacts.html) that may be confidential, >> proprietary copyrighted and/or legally privileged. It is intended solely >> for the use of the individual or entity named on this message. If you are >> not the intended recipient, and have received this message in error, >> please notify us immediately by reply e-mail and then delete it from >> your system. >
