title: Structural and functional analysis of HtrA1 and its subdomains.
abstract: The homotrimeric human serine protease HtrA1 is homologous to bacterial HtrA proteases regarding the trypsin-like catalytic and PDZ domains but differs by the presence of an N-terminal domain with IGFBP and Kazal homology. The crystal structures and SAXS analysis presented herein reveal the rare tandem of IGFBP- and Kazal-like modules, a protease active site that adopts a competent conformation in the absence of substrate or inhibitor and a model for the intact protein in solution. Highly sensitive enzymatic assays and binding studies demonstrate that the N-terminal tandem has no apparent effect on protease activity, and in accordance with the structure-based predictions, neither the IGFBP- nor Kazal-like module retains the function of their prototype proteins. Our structures of the unliganded HtrA1 active site suggest two-state equilibrium and a "conformational selection" model, in which substrate binds to the active conformer.
authors.affiliation: Department of Structural Biology, Genentech, Inc., South San Francisco, CA 94080, USA.
authors.forename: Charles
authors.initials: C
authors.lastname: Eigenbrot
authors.forename: Mark
authors.initials: M
authors.lastname: Ultsch
authors.forename: Michael T
authors.initials: MT
authors.lastname: Lipari
authors.forename: Paul
authors.initials: P
authors.lastname: Moran
authors.forename: S Jack
authors.initials: SJ
authors.lastname: Lin
authors.forename: Rajkumar
authors.initials: R
authors.lastname: Ganesan
authors.forename: Clifford
authors.initials: C
authors.lastname: Quan
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Tom
authors.forename: Wendy
authors.initials: W
authors.lastname: Sandoval
authors.forename: Menno
authors.initials: M
authors.lastname: van Lookeren Campagne
authors.forename: Daniel
authors.initials: D
authors.lastname: Kirchhofer
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001059:Apoproteins / Q000737:chemistry; D020134:Catalytic Domain; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D000074289:High-Temperature Requirement A Serine Peptidase 1; D006801:Humans; D006860:Hydrogen Bonding; D007531:Isoflurophate / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D017433:Protein Structure, Secondary; D053838:Scattering, Small Angle; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000235:genetics; D015842:Serine Proteinase Inhibitors / Q000737:chemistry; D013379:Substrate Specificity; D013499:Surface Properties
chemical_list: D001059:Apoproteins; D015842:Serine Proteinase Inhibitors; D007531:Isoflurophate; D000074289:High-Temperature Requirement A Serine Peptidase 1; C474012:HTRA1 protein, human; D012697:Serine Endopeptidases