If you have access to a mass spec/proteomics facility, it should be easy to get an intact mass on your protein followed by N-terminal sequencing using MS/MS.
If your sequence begins with a Met-Ser, then it is likely that the N-terminal Met is cleaved and the Ser is acetylated. Roopa Thapar On Fri, November 16, 2007 1:41 pm, Yong, Wei wrote: > Dear all, > > I solved a protein crystal structure which is about 95KD and was purified > from pig liver. Based on the crystal structure, I missed 36 residues at > its N-terminus and 16 at its C-terminus. I tried to do N-terminus > sequencing to identify if these 36 residues was cleaved or not. However, > the N-terminus sequencing failed. One of the possibilities is that the > N-terminus has been blocked by some post-translational modifications, such > as acetylation and methylation, which leave no free NH2 group. Can anybody > give me some suggestions about how I can deblock the modifications so that > I can do N-terminus sequencing? Or any other suggestions on how to > identify from which residue my protein starts (Other techniques). > > Thanks you very much in advance. > > Best wishes > > Wei Yong > -- Roopa Thapar Assistant Professor, University of North Carolina Visiting Scientist, Hauptman-Woodward Institute 700 Ellicott Street, Buffalo, NY 14203
