title: Crystal structure of a clip-domain serine protease and functional roles of the clip domains.
abstract: Clip-domain serine proteases (SPs) are the essential components of extracellular signaling cascades in various biological processes, especially in embryonic development and the innate immune responses of invertebrates. They consist of a chymotrypsin-like SP domain and one or two clip domains at the N-terminus. Prophenoloxidase-activating factor (PPAF)-II, which belongs to the noncatalytic clip-domain SP family, is indispensable for the generation of the active phenoloxidase leading to melanization, a major defense mechanism of insects. Here, the crystal structure of PPAF-II reveals that the clip domain adopts a novel fold containing a central cleft, which is distinct from the structures of defensins with a similar arrangement of cysteine residues. Ensuing studies demonstrated that PPAF-II forms a homo-oligomer upon cleavage by the upstream protease and that the clip domain of PPAF-II functions as a module for binding phenoloxidase through the central cleft, while the clip domain of a catalytically active easter-type SP plays an essential role in the rapid activation of its protease domain.
authors.affiliation: National Research Laboratory of Defense Proteins, College of Pharmacy and Research Institute for Drug Development, Pusan National University, Jangjeon Dong, Geumjeong Gu, Busan, Korea.
authors.forename: Shunfu
authors.initials: S
authors.lastname: Piao
authors.forename: Young-Lan
authors.initials: YL
authors.lastname: Song
authors.forename: Jung Hyun
authors.initials: JH
authors.lastname: Kim
authors.forename: Sam Yong
authors.initials: SY
authors.lastname: Park
authors.forename: Ji Won
authors.initials: JW
authors.lastname: Park
authors.forename: Bok Leul
authors.initials: BL
authors.lastname: Lee
authors.forename: Byung-Ha
authors.initials: BH
authors.lastname: Oh
authors.forename: Nam-Chul
authors.initials: NC
authors.lastname: Ha
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016367:Baculoviridae / Q000378:metabolism; D020134:Catalytic Domain; D004156:Catechol Oxidase / Q000737:chemistry; D002845:Chromatography; D002918:Chymotrypsin / Q000737:chemistry; D001517:Coleoptera; D018360:Crystallography, X-Ray; D004330:Drosophila; D004792:Enzyme Precursors / Q000737:chemistry; D007313:Insecta; D008854:Microscopy, Electron; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D004792:Enzyme Precursors; D011994:Recombinant Proteins; C038451:pro-phenoloxidase; D004156:Catechol Oxidase; D012697:Serine Endopeptidases; C022435:prephenoloxidase-activating enzyme; D002918:Chymotrypsin