title: A true autoactivating enzyme. Structural insight into mannose-binding lectin-associated serine protease-2 activations.
abstract: Few reports have described in detail a true autoactivation process, where no extrinsic cleavage factors are required to initiate the autoactivation of a zymogen. Herein, we provide structural and mechanistic insight into the autoactivation of a multidomain serine protease: mannose-binding lectin-associated serine protease-2 (MASP-2), the first enzymatic component in the lectin pathway of complement activation. We characterized the proenzyme form of a MASP-2 catalytic fragment encompassing its C-terminal three domains and solved its crystal structure at 2.4 A resolution. Surprisingly, zymogen MASP-2 is capable of cleaving its natural substrate C4, with an efficiency about 10% that of active MASP-2. Comparison of the zymogen and active structures of MASP-2 reveals that, in addition to the activation domain, other loops of the serine protease domain undergo significant conformational changes. This additional flexibility could play a key role in the transition of zymogen MASP-2 into a proteolytically active form. Based on the three-dimensional structures of proenzyme and active MASP-2 catalytic fragments, we present model for the active zymogen MASP-2 complex and propose a mechanism for the autoactivation process.
authors.affiliation: Institute of Enzymology, Biological Research Center, Hungarian Academy of Sciences, P.O. Box 7, Budapest H-1518, Hungary.
authors.forename: Péter
authors.initials: P
authors.lastname: Gál
authors.forename: Veronika
authors.initials: V
authors.lastname: Harmat
authors.forename: Andrea
authors.initials: A
authors.lastname: Kocsis
authors.forename: Tünde
authors.initials: T
authors.lastname: Bián
authors.forename: László
authors.initials: L
authors.lastname: Barna
authors.forename: Géza
authors.initials: G
authors.lastname: Ambrus
authors.forename: Barbara
authors.initials: B
authors.lastname: Végh
authors.forename: Júlia
authors.initials: J
authors.lastname: Balczer
authors.forename: Robert B
authors.initials: RB
authors.lastname: Sim
authors.forename: Gábor
authors.initials: G
authors.lastname: Náray-Szabó
authors.forename: Péter
authors.initials: P
authors.lastname: Závodszky
mesh_terms: D001665:Binding Sites; D002152:Calorimetry, Differential Scanning; D003181:Complement C4 / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D004795:Enzyme Stability; D006207:Half-Life; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D037601:Mannose-Binding Lectin / Q000378:metabolism*; D050606:Mannose-Binding Protein-Associated Serine Proteases / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008954:Models, Biological; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000378:metabolism*; D013820:Thermolysin / Q000494:pharmacology
chemical_list: D003181:Complement C4; D037601:Mannose-Binding Lectin; D011994:Recombinant Proteins; C105296:MASP2 protein, human; D050606:Mannose-Binding Protein-Associated Serine Proteases; D012697:Serine Endopeptidases; D013820:Thermolysin