Human OS-9 MRH domain complexed with alpha3,alpha6-Man5
[OS9_HUMAN] Lectin which functions in endoplasmic reticulum (ER) quality control and ER-associated degradation (ERAD). May bind terminally misfolded non-glycosylated proteins as well as improperly folded glycoproteins, retain them in the ER, and possibly transfer them to the ubiquitination machinery and promote their degradation. Possible targets include TRPV4.     
Publication Abstract from PubMed
Misfolded glycoproteins are translocated from endoplasmic reticulum (ER) into the cytosol for proteasome-mediated degradation. A mannose-6-phosphate receptor homology (MRH) domain is commonly identified in a variety of proteins and, in the case of OS-9 and XTP3-B, is involved in glycoprotein ER-associated degradation (ERAD). Trimming of outermost alpha1,2-linked mannose on C-arm of high-mannose-type glycan and binding of processed alpha1,6-linked mannosyl residues by the MRH domain are critical steps in guiding misfolded glycoproteins to enter ERAD. Here we report the crystal structure of a human OS-9 MRH domain (OS-9(MRH)) complexed with alpha3,alpha6-mannopentaose. The OS-9(MRH) has a flattened beta-barrel structure with a characteristic P-type lectin fold and possesses distinctive double tryptophan residues in the oligosaccharide-binding site. Our crystallographic result in conjunction with nuclear magnetic resonance (NMR) spectroscopic and biochemical results provides structural insights into the mechanism whereby OS-9 specifically recognizes Manalpha1,6Manalpha1,6Man residues on the processed C-arm through the continuous double tryptophan (WW) motif.
Structural Basis for Oligosaccharide Recognition of Misfolded Glycoproteins by OS-9 in ER-Associated Degradation.,Satoh T, Chen Y, Hu D, Hanashima S, Yamamoto K, Yamaguchi Y Mol Cell. 2010 Dec 22;40(6):905-16. PMID:21172656
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.