differential glycosylation

Iain Wilson iwilson at molbiol.ox.ac.uk
Mon Aug 1 07:21:55 EST 1994

In article <dudleyd-190794172405 at dom022.dom.aa.wl.com>, dudleyd at aa.wl.com (Dave Dudley) writes:
> In article <30etpi$kqt at larry.rice.edu>, (babette schmansky) wrote:
>> There are plenty of examples of glycoproteins that _lose_ their activity or
>> specificity when they are deglycosylated or expressed in bacteria, but can
>> anyone tell me of specific proteins that _change_ their funtion under
>> different glycosylation patterns.  For example, a ligand that specifically
>> binds one receptor when glycosylated and another when not glycosylated.
>> Responses posted to the group would be fine.
>> Thanks
> I don't know of any specific answers to your query.  But, I'll add another
> horn to your dilemma...I work with a membrane receptor for a small peptide.
>  This particular receptor appears to have widely varying glycosylation
> patterns (and in some cases accounting for up to 75% of the mass of the
> beast), yet no apparent difference in binding activity.
> -- 
> Dave Dudley (dudleyd at aa.wl.com)
> Parke-Davis/Signal Transduction
> Ann Arbor, MI, USA

Probably the most exhaustive literature review on the subject of the function 
of glycosylation appeared in the journal 'Glycobiology' last year - A. Varki, 
Biological roles of oligosaccharides: all of the theories are correct, 1993, 
Glycobiology, Vol. 3, pp. 97-130. 

Sometimes, differential glycosylation does have an effect on kinetics of an 
enzyme (e.g. the difference between the doubly and triply glycosylated forms 
of tissue plasminogen activator). Often glycosylation merely reflects the 
range of glycosyltransferases in the particular tissue and is of no function 
other than (perhaps) increasing stability or altering biological half-life. 
Sometimes the glycosylation creates new ligands (e.g. sialyl Lewis X) which 
have specific functions - and if you had a different type of glycosylation 
then a different lectin would recognise the glycoprotein. So there are no 
clear-cut answers!!
Iain Wilson				Dyson Perrins Laboratory
Postdoctoral Research Assistant		University of Oxford
Tel: +44-865-275696			South Parks Road, Oxford, OX1 3QY, UK
Fax: +44-865-275674			E-mail: iwilson at molbiol.ox.ac.uk

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