PTM is very much possible in E. coli - just not every kind of PTM. To my knowledge, serine, threonine, and tyrosine phosphorylation is not in the normal genetic arsenal of this organism unless you introduce appropriate kinases artificially (such as by means of expression of a foreign gene or via modification of a suitable E. coli enzyme).
If you express a kinase, there are good chances that it will phosphorylate itself and many other intracellular proteins. Other than that, you may encounter instances of histidine phosphorylation. Artem -----Original Message----- From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On Behalf Of Narayanan Ramasubbu Sent: Friday, October 26, 2007 6:31 PM To: [email protected] Subject: [ccp4bb] Is phophorylation possible in E. coli expression system? Dear All: This is not crystallography related and does not belong to this group, but I would like to pose this to all who are working with proteins expressed in an E. coli BL21 (DE3) or Rosetta. Is it possible for a protein to be phosphorylated during expression? At least my understanding was that post-translational modifications are not possible in E. coli. However, recently we expressed a protein and noticing that there are lot of potential tyrosine phosphorylation sites, we checked the expressed protein on a gel using a stain that detect phosphates. (Please do not say Are you crazy? Why would you check.. etc). Lo and behold, there lights up the band. Hence my question to you all. I could not google or mine from PubMed specific references that exist regarding this. Please enlighten me. Thanks a lot. Also, I would like to take this opportunity to thank everybody for all the help whenever ask some off-topic question like ths. Subbu
