Estimating Loop−Helix Interfaces in a Polytopic Membrane Protein by Deletion Analysis†

Biochemistry ◽  
1999 ◽  
Vol 38 (26) ◽  
pp. 8590-8597 ◽  
Author(s):  
Christopher D. Wolin ◽  
H. Ronald Kaback
Keyword(s):  
Membrane Protein ◽  
Deletion Analysis ◽  
Polytopic Membrane Protein

Escherichia coliDiacylglycerol Kinase Is an α-Helical Polytopic Membrane Protein and Can Spontaneously Insert into Preformed Lipid Vesicles†

Biochemistry ◽  
1996 ◽  
Vol 35 (26) ◽  
pp. 8610-8618 ◽  
Author(s):  
Charles R. Sanders ◽  
Lech Czerski ◽  
Olga Vinogradova ◽  
Prakash Badola ◽  
David Song ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Lipid Vesicles ◽  
Polytopic Membrane Protein

scholarly journals Endoplasmic reticulum transmembrane protein TMTC3 contributes to O-mannosylation of E-cadherin, cellular adherence, and embryonic gastrulation

2020 ◽  
Vol 31 (3) ◽  
pp. 167-183 ◽  
Author(s):  
Jill B. Graham ◽  
Johan C. Sunryd ◽  
Ketan Mathavan ◽  
Emma Weir ◽  
Ida Signe Bohse Larsen ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Protein ◽  
Transmembrane Protein ◽  
Homophilic Binding ◽  
Polytopic Membrane Protein ◽  
E Cadherin

Here we characterize TMTC3 as an ER, polytopic membrane protein with C-terminal luminal-facing TPRs, and an O-mannosyltransferase of E-cadherin. O-mannosylation of cadherins by TMTC3 affects cellular adherence, E-cadherin homophilic binding, and embryonic gastrulation, helping to explain the basis of a number of TMTC3-associated disease variants.

scholarly journals Dissecting the ER-Associated Degradation of a Misfolded Polytopic Membrane Protein

Cell ◽  
2008 ◽  
Vol 132 (1) ◽  
pp. 101-112 ◽  
Author(s):  
Kunio Nakatsukasa ◽  
Gregory Huyer ◽  
Susan Michaelis ◽  
Jeffrey L. Brodsky
Keyword(s):  
Membrane Protein ◽  
Polytopic Membrane Protein

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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