Re: Posttranslational Modifications

Chris West (westcm@anatomy.med.ufl.edu)
Wed, 29 Jul 1998 14:50:06 -0500

>In "the other Ken's" original post, he stated the doublet ran "about twice
>the distance between the phospho and non-phosho forms of either individual
>species" in isoelectric focussing.
>
>Gerald Hart presented his "dynamic glycosylation" data at Lorne this year
>and we have been looking out for it in some of the regulatory systems we
>are interested in. I am curious if you, or anyone else out there, knows how
>GlcNacylation would be expected to affect the isoelectric mobility of a
>protein?
>
>regards....Ken Mitchelhill
>
>>Ken
>>
>>An interesting possibility for a PTM would be attachment of a single
>>hexosamine (+161). Gerald Hart has found that specific glycation (with
>>GlcNac I think) acts to limit phosphorylation.
>>
>>Ken

In case this isn't clear, the modification is an N-acetyl-glucosamine
(GlcNAc) which is neutral and would not add a charge, and would add a mass
of 202. This is an example of glycosylation, with the term glycation
usually reserved for non-enzymatic addition of glucose or other sugars to
amino groups. I am not aware of any instances of de-N-acetylation. There is
also no charge effect from its attachment to the hydroxyl of Ser or Thr
residues. However, there is evidence that this modification is reversible
and can compete with phosphorylation of the same or nearby Ser/Thr
residues, which would be expected to have isoelectric mobility
consequences. Regards, -Chris
Christopher M. West, Ph.D.
Associate Professor of Anatomy & Cell Biology
Scientific Director, ICBR Glycobiology Core
University of Florida College of Medicine
Gainesville, FL 32610-0235

Ph 352-392-3329
Fax 352-392-3305
email westcm@anatomy.med.ufl.edu