1hcn
STRUCTURE OF HUMAN CHORIONIC GONADOTROPIN AT 2.6 ANGSTROMS RESOLUTION FROM MAD ANALYSIS OF THE SELENOMETHIONYL PROTEIN
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OverviewOverview
BACKGROUND: Human chorionic gonadotropin (hCG) is a placental hormone that, stimulates secretion of the pregnancy-sustaining steroid progesterone. It, is a member of a family of glycoprotein hormones that are disulfide-rich, heterodimers, with a common alpha-chain and distinctive beta-chains, specific to their particular G-protein linked receptors. RESULTS: We have, produced recombinant hCG in mammalian cells as the selenomethionyl, protein, and have determined its structure (after partial deglycosylation), at 2.6 A resolution from multiwavelength anomalous diffraction (MAD), measurements. Despite only limited sequence similarity (10% identity), the, alpha- and beta-subunits of hCG have similar tertiary folds. Each subunit, has a cystine-knot motif at its core of extended hairpin loops. There is a, very extensive subunit interface featuring two inter-chain beta-sheets and, a unique, disulfide-tethered 'arm' from the beta-subunit which 'embraces', the alpha-subunit. The carboxy-terminal peptide of the beta-subunit, which, is rich in O-linked sugars, is disordered. CONCLUSIONS: Structural and, sequence comparisons indicate an evolutionary homology, albeit remote, between the glycoprotein hormone chains and other cystine-knot proteins, notably platelet-derived growth factor. Segments of the alpha- and, beta-chains that have been convincingly implicated in receptor binding by, hCG are juxtaposed on one side of the molecule. A glycosylation site, implicated in signal transduction but not in binding is also close to the, presumed binding site suggesting a possible coupling between ligand, binding and signaling. This study with selenomethionyl protein produced in, mammalian cells extends the realm of MAD phasing.
About this StructureAbout this Structure
1HCN is a Protein complex structure of sequences from [1] with NAG as ligand. Full crystallographic information is available from OCA.
ReferenceReference
Structure of human chorionic gonadotropin at 2.6 A resolution from MAD analysis of the selenomethionyl protein., Wu H, Lustbader JW, Liu Y, Canfield RE, Hendrickson WA, Structure. 1994 Jun 15;2(6):545-58. PMID:7922031
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