N-linkage efficiency/selectivity

Mon Jun 16 18:52:08 EST 1997

Lou Hom wrote on June 11: 

In Alberts, they say that the initial attachment of the 14-sugar complex to
Asn's in the ER happens rapidly . . . something like "most proteins are
glycosylated as they are translocated".  Anyway, the important part was the
"most" -- does anyone have an idea what "most" means?  Does it have to do
with kinetics or selectivity or both?   

Dr. Barbara Imperiali, a chemistry professor at CalTech extensively studied
the mechanism of N-glycosylation by using synthetic inhibitors to oligo-
saccharyltransferase, the enzyme that en bloc transfers GlcNAc2Hex12 from its
lipid carrier to nacent polypeptide.  They worked out a catalysis mechanism
for this key enzyme (J. Am. Chem. Soc. 118: 7636, 1996).  

As everyone knows there is a consensus sequence for N-glycosylation, Asn-Xaa- 
Ser/Thr, where Xaa could be any amino acid except Pro.  However, such a 
sequence does not necessarily mandate an aquisition of an oligosaccharide.

I hope someone else could provide more detailed input on this question.

* Ke-Wei Zhao, Ph.D.                     Phone: (310)825-8722       
* Department of Biological Chemistry     Fax: (310)206-5272
* UCLA School of Medicine, CHS 33-257    e-mail: kzhao at biovx1.biology.ucla.edu
* Los Angeles, CA 90095-1737

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