2a70
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Crystal structure of Emp47p carbohydrate recognition domain (CRD), monoclinic crystal form 2
OverviewOverview
Emp46p and Emp47p are type I membrane proteins, which cycle between the, endoplasmic reticulum (ER) and the Golgi apparatus by vesicles coated with, coat protein complexes I and II (COPI and COPII). They are considered to, function as cargo receptors for exporting N-linked glycoproteins from the, ER. We have determined crystal structures of the carbohydrate recognition, domains (CRDs) of Emp46p and Emp47p of Saccharomyces cerevisiae, in the, absence and presence of metal ions. Both proteins fold as a beta-sandwich, and resemble that of the mammalian ortholog, p58/ERGIC-53. However, the, nature of metal binding is distinct from that of Ca(2+)-dependent, p58/ERGIC-53. Interestingly, the CRD of Emp46p does not bind Ca(2+) ion, but instead binds K(+) ion at the edge of a concave beta-sheet whose, position is distinct from the corresponding site of the Ca(2+) ion in, p58/ERGIC-53. Binding of K(+) ion to Emp46p appears essential for, transport of a subset of glycoproteins because the Y131F mutant of Emp46p, which cannot bind K(+) ion fails to rescue the transport in disruptants of, EMP46 and EMP47 genes. In contrast the CRD of Emp47p binds no metal ions, at all. Furthermore, the CRD of Emp46p binds to glycoproteins carrying, high mannosetype glycans and the is promoted by binding not the addition, of Ca(2+) or K(+) ion in These results suggest that Emp46p can be regarded, as a Ca(2+)-independent intracellular lectin at the ER exit sites.
About this StructureAbout this Structure
2A70 is a Single protein structure of sequence from Saccharomyces cerevisiae with EDO as ligand. Full crystallographic information is available from OCA.
ReferenceReference
Structures of the carbohydrate recognition domain of Ca2+-independent cargo receptors Emp46p and Emp47p., Satoh T, Sato K, Kanoh A, Yamashita K, Yamada Y, Igarashi N, Kato R, Nakano A, Wakatsuki S, J Biol Chem. 2006 Apr 14;281(15):10410-9. Epub 2006 Jan 26. PMID:16439369
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