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Licensed Unlicensed Requires Authentication Published by De Gruyter June 1, 2005

O-Glycosylation of the Mucin Type

  • Franz-Georg Hanisch
From the journal Biological Chemistry

Abstract

While only about ten percent of the databank entries are defined as glycoproteins, it has been estimated recently that more than half of all proteins are glycoproteins. Mucintype Oglycosylation is a widespread posttranslational modification of proteins found in the entire animal kingdom, but also in higher plants. The structural complexity of the chains initiated by Olinked GalNAc exceeds that of Nlinked chains by far. The process during which serine and threonine residues of proteins become modified is confined to the cis to trans Golgi compartments. The initiation of this process by peptidyl GalNActransferases is ruled by the sequence context of putative Oglycosylation sites, but also by epigenetic regulatory mechanisms, which can be mediated by enzyme competition. The cellular repertoir of glycosyltransferases with their distinct donor sugar and acceptor sugar specificities, their sequential action at highlyordered surfaces, and their localizations in subcompartments of the Golgi finally determine the cellspecific Oglycosylation profile. Dramatic alterations of the glycosylation machinery are observed in cancer cells, resulting in aberrantly Oglycosylated proteins that expose previously masked peptide motifs and new antigenic targets. The functional aspects of Olinked glycans, which comprise among many others their potential role in sorting and secretion of glycoproteins, their influence on protein conformation, and their multifarious involvement in cell adhesion and immunological processes, appear as complex as their structures.

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Published Online: 2005-06-01
Published in Print: 2001-02-12

Copyright © 2001 by Walter de Gruyter GmbH & Co. KG

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