protein modification (fwd)

[MJ Duggan]

> 
> Hello dear friends
> 
> I try again a difficult question:
> Is there any information somehere on known sequences in
> proteins suceptible to be post-translationelly modified, that would concern a Serine in the sequence KSSK. And would lead to a shift in mobility
> of several Kda.  
> 
> 
> Thanks networkers
> 
What is the residue N-terminal of this? If it is Asparagine then the
Ser could be contributing to the N-linked glycosylation site.
What about O-linked glycosylation? 
Am I right in assuming that the post-translational modification is
leading to an increase in the MW?

More information would make it easier to help.

Mike Duggan