A catalytically essential motif in external loop 5 of the bacterial oligosaccharyltransferase PglB.

ABSTRACT: Asparagine-linked glycosylation is a post-translational protein modification that is conserved in all domains of life. The initial transfer of a lipid-linked oligosaccharide (LLO) onto acceptor asparagines is catalyzed by the integral membrane protein oligosaccharyltransferase (OST). The previously reported structure of a single-subunit OST enzyme, the Campylobacter lari protein PglB, revealed a partially disordered external loop (EL5), whose role in catalysis was unclear. We identified a new and functionally important sequence motif in EL5 containing a conserved tyrosine residue (Tyr293) whose aromatic side chain is essential for catalysis. A synthetic peptide containing the conserved motif can partially but specifically rescue in vitro activity of mutated PglB lacking Tyr293. Using site-

SUBMITTER: Lizak C 

PROVIDER: S-EPMC3887201 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature