title: Identification and characterization of a novel factor XIIa inhibitor in the hematophagous insect, Triatoma infestans (Hemiptera: Reduviidae).
abstract: Recently, we have cloned several Kazal-type serine protease inhibitors from the midgut of the Triatoma infestans bug. A single gene composed of multi Kazal-type domains, in tandem, encodes these inhibitors. In this work, we describe the purification and characterization of recombinant infestins 3-4 and 4, which are potent factor XIIa inhibitors (KI=67 pM and 128 pM, respectively). We also identified the first native factor XIIa inhibitor from a hematophagous insect. The factor XIIa inhibitory activity of infestin 4 demonstrates extremely efficient anticoagulant activity, prolonging activated partial thromboplastin time by approximately 3 times. Our results suggest that infestins perform a very important role in the T. infestans midgut during meal acquisition and digestion by controlling blood coagulation by means of inhibiting thrombin and factor XIIa.
authors.affiliation: Department of Biochemistry, Universidade Federal de São Paulo, Rua Tres de Maio 100, 04044-020, São Paulo, Brazil.
authors.forename: Ivan T N
authors.initials: IT
authors.lastname: Campos
authors.forename: Anita M
authors.initials: AM
authors.lastname: Tanaka-Azevedo
authors.forename: Aparecida S
authors.initials: AS
authors.lastname: Tanaka
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000925:Anticoagulants / Q000494:pharmacology; D001769:Blood / Q000187:drug effects; D001798:Blood Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D002852:Chromatography, Ion Exchange; D003001:Cloning, Molecular; D015870:Gene Expression; D006430:Hemiptera / Q000737:chemistry*; D006801:Humans; D019476:Insect Proteins / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D010314:Partial Thromboplastin Time; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D020064:Reduviidae / Q000737:chemistry*; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D014224:Triatoma / Q000737:chemistry*
chemical_list: D000925:Anticoagulants; D001798:Blood Proteins; D019476:Insect Proteins; D011994:Recombinant Proteins; C053635:factor XIIa inhibitor; C467902:infestin protein, Triatoma infestans