title: Binding characteristics of thrombin-activatable fibrinolysis inhibitor to streptococcal surface collagen-like proteins A and B.
abstract: Streptococcus pyogenes  is the causative agent in a wide range of diseases in humans. Thrombin-activatable fibrinolysis inhibitor (TAFI) binds to collagen-like proteins SclA and SclB at the surface of  S. pyogenes. Activation of TAFI at this surface redirects inflammation from a transient to chronic state by modulation of the kallikrein/kinin system. We investigated TAFI binding characteristics to SclA/SclB. Thirty-four overlapping TAFI peptides of ~20 amino acids were generated. Two of these peptides (P18: residues G205-S221, and P19: R214-D232) specifically bound to SclA/SclB with high affinity, and competed in a dose-dependent manner with TAFI binding to SclA/SclB. In another series of experiments, the binding properties of activated TAFI (TAFIa) to SclA/SclB were studied with a quadruple TAFI mutant (TAFI-IIYQ) that after activation is a 70-fold more stable enzyme than wild-type TAFIa. TAFI and TAFI-IIYQ bound to the bacterial proteins with similar affinities. The rate of dissociation was different between the proenzyme (both TAFI and TAFI-IIYQ) and the stable enzyme TAFIa-IIYQ. TAFIa-IIYQ bound to SclA/SclB, but dissociated faster than TAFI-IIYQ. In conclusion, the bacterial proteins SclA and SclB bind to a TAFI fragment encompassing residues G205-D232. Binding of TAFI to the bacteria may allow activation of TAFI, whereafter the enzyme easily dissociates.
authors.affiliation: Department of Experimental Vascular Medicine, Academic Medical Center, Amsterdam, The Netherlands.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Valls Serón
authors.forename: Tom
authors.initials: T
authors.lastname: Plug
authors.forename: J Arnoud
authors.initials: JA
authors.lastname: Marquart
authors.forename: Pauline F
authors.initials: PF
authors.lastname: Marx
authors.forename: Heiko
authors.initials: H
authors.lastname: Herwald
authors.forename: Philip G
authors.initials: PG
authors.lastname: de Groot
authors.forename: Joost C M
authors.initials: JC
authors.lastname: Meijers
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001778:Blood Coagulation Disorders / Q000097:blood* / Q000209:etiology / Q000382:microbiology; D025901:Carboxypeptidase B2 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D005098:Exotoxins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D055550:Protein Stability; D013290:Streptococcal Infections / Q000097:blood* / Q000150:complications / Q000382:microbiology; D013297:Streptococcus pyogenes / Q000378:metabolism / Q000472:pathogenicity*; D013917:Thrombin / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D005098:Exotoxins; D008565:Membrane Proteins; D010446:Peptide Fragments; C117980:SpeA protein, Streptococcus pyogenes; C027951:erythrogenic toxin; D025901:Carboxypeptidase B2; D013917:Thrombin