title: Crystal structure of the cysteine-rich secretory protein stecrisp reveals that the cysteine-rich domain has a K+ channel inhibitor-like fold.
abstract: Stecrisp from Trimeresurus stejnegeri snake venom belongs to a family of cysteine-rich secretory proteins (CRISP) that have various functions related to sperm-egg fusion, innate host defense, and the blockage of ion channels. Here we present the crystal structure of stecrisp refined to 1.6-angstrom resolution. It shows that stecrisp contains three regions, namely a PR-1 (pathogenesis-related proteins of group1) domain, a hinge, and a cysteine-rich domain (CRD). A conformation of solvent-exposed and -conserved residues (His60, Glu75, Glu96, and His115) in the PR-1 domain similar to that of their counterparts in homologous structures suggests they may share some molecular mechanism. Three flexible loops of hypervariable sequence surrounding the possible substrate binding site in the PR-1 domain show an evident difference in homologous structures, implying that a great diversity of species- and substrate-specific interactions may be involved in recognition and catalysis. The hinge is fixed by two crossed disulfide bonds formed by four of ten characteristic cysteines in the carboxyl-terminal region and is important for stabilizing the N-terminal PR-1 domain. Spatially separated from the PR-1 domain, CRD possesses a similar fold with two K+ channel inhibitors (Bgk and Shk). Several candidates for the possible functional sites of ion channel blocking are located in a solvent-exposed loop in the CRD. The structure of stecrisp will provide a prototypic architecture for a structural and functional exploration of the diverse members of the CRISP family.
authors.affiliation: Key Laboratory of Structural Biology, Department of Molecular and Cell Biology, School of Life Sciences, Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, China.
authors.forename: Min
authors.initials: M
authors.lastname: Guo
authors.forename: Maikun
authors.initials: M
authors.lastname: Teng
authors.forename: Liwen
authors.initials: L
authors.lastname: Niu
authors.forename: Qun
authors.initials: Q
authors.lastname: Liu
authors.forename: Qingqiu
authors.initials: Q
authors.lastname: Huang
authors.forename: Quan
authors.initials: Q
authors.lastname: Hao
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002845:Chromatography; D003435:Crotalid Venoms / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry*; D004220:Disulfides / Q000737:chemistry; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D015221:Potassium Channels / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D003435:Crotalid Venoms; D004220:Disulfides; D046911:Macromolecular Substances; D015221:Potassium Channels; C495582:stecrisp protein, Trimeresurus stejnegeri; D003545:Cysteine