oligosaccharyl transferase

2020 ◽  
Author(s):  
C.‐H. Wong
Keyword(s):  
Oligosaccharyl Transferase

scholarly journals Studies on oligosaccharyl transferase in yeast.

2007 ◽  
Vol 54 (4) ◽  
pp. 673-677 ◽  
Author(s):  
William J Lennarz
Keyword(s):  
Crystal Structure ◽  
Essential Genes ◽  
Oligosaccharyl Transferase ◽  
Transmembrane Segments ◽  
Eukaryotic Organisms ◽  
Lumenal Domain

In yeast, OT consists of nine different subunits, all of which contain one or more predicted transmembrane segments. In yeast, five of these proteins are encoded by essential genes, Swp1p, Wbp1p, Ost2p, Ost1p and Stt3p. Four others are not essential Ost3p, Ost4p, Ost5p, Ost6p. All yeast OT subunits have been cloned and sequenced (Kelleher et al., 1992; 2003; Kelleher & Gilmore, 1997; Kumar et al., 1994; 1995; Breuer & Bause, 1995) and the structure of one of them, Ost4p, has been solved by NMR (Zubkov et al., 2004). Very recently, the preliminary crystal structure of the lumenal domain of an archaeal Stt3p homolog has been reported (Mayumi et al., 2007). Homologs of all OT subunits have been identified in higher eukaryotic organisms (Kelleher et al., 1992; 2003; Kumar et al., 1994; Kelleher & Gilmore, 1997).

scholarly journals Studies on the Function of Oligosaccharyl Transferase Subunits

2002 ◽  
Vol 277 (49) ◽  
pp. 47692-47700 ◽  
Author(s):  
Qi Yan ◽  
William J. Lennarz
Keyword(s):  
Oligosaccharyl Transferase

scholarly journals Glycosylation of multiple extracytosolic loops in Band 3, a model polytopic membrane protein

1996 ◽  
Vol 318 (2) ◽  
pp. 645-648 ◽  
Author(s):  
Lisa Y TAM ◽  
Carolina LANDOLT-MARTICORENA ◽  
Reinhart A. F. REITHMEIER
Keyword(s):  
Membrane Proteins ◽  
Membrane Protein ◽  
Band 3 ◽  
Site Directed Mutagenesis ◽  
Acceptor Site ◽  
Oligosaccharyl Transferase ◽  
Transmembrane Segments ◽  
Free Translation ◽  
Reticulocyte Lysates ◽  
Polytopic Membrane Protein

N-glycosylated sites in polytopic membrane proteins are usually localized to single extracytosolic (EC) loops containing more than 30 residues [Landolt-Marticorena and Reithmeier (1994) Biochem. J. 302, 253–260]. This may be due to a biosynthetic restriction whereby only a single loop of nascent polypeptide is available to the oligosaccharyl transferase in the lumen of the endoplasmic reticulum. To test this hypothesis, two types of N-glycosylation mutants were constructed using Band 3, a polytopic membrane protein that contains up to 14 transmembrane segments and a single endogenous site of N-glycosylation at Asn-642 in EC loop 4. In the first set of mutants, an additional N-glycosylation acceptor site (Asn-Xaa-Ser/Thr) was constructed by site-directed mutagenesis in EC loop 3, with or without retention of the endogenous site. In the second set of mutants, EC loop 4 was duplicated and inserted into EC loop 2, again with or without retention of the endogenous site. Cell-free translation experiments using reticulocyte lysates showed that microsomes were able to N-glycosylate multiple EC loops in these Band 3 mutants. The acceptor site in EC loop 3 was poorly N-glycosylated, probably due to the suboptimal size (25 residues) of this EC loop. The localization of N-glycosylation sites to single EC loops in multi-span membrane proteins is probably due to the absence of suitably positioned acceptor sites on multiple loops.

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