title: Fibrinogen gamma' chain binds thrombin exosite II.
abstract: A high-affinity thrombin-binding site in an alternately processed fibrinogen variant, the gammaA/gamma' isoform, is characterized in this report. The binding site has been shown to be situated between gamma' 414 and 427, and Tyr418 and 422 in this part of the gamma' chain are known to be sulfated. A synthetic peptide corresponding to the gamma' chain carboxyl terminus is shown to bind thrombin with a Kd = 0.63 +/- 0.16 micro mol L-1. Maximum binding of this peptide requires negative charges on Tyr418 and 422. Competitive binding studies with hirudin peptides, heparin and DNA aptamers specific for thrombin exosites I or II indicate thrombin binds to the gamma' peptide via exosite II. Thus, thrombin binding to the gamma' chain leaves exosite I and the active site accessible to substrates. This may explain why fibrin-bound thrombin can retain enzymatic activity, and why fibrin-bound thrombin is heparin-resistant.
authors.affiliation: Department of Pathology, School of Medicine, Oregon Health and Science University, Portland, Oregon 97239-3098, USA.
authors.forename: R S
authors.initials: RS
authors.lastname: Lovely
authors.forename: M
authors.initials: M
authors.lastname: Moaddel
authors.forename: D H
authors.initials: DH
authors.lastname: Farrell
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D002460:Cell Line; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D005340:Fibrinogen / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D006493:Heparin / Q000737:chemistry / Q000378:metabolism; D006629:Hirudins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D013917:Thrombin / Q000737:chemistry / Q000378:metabolism*; D014162:Transfection; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism
chemical_list: D006629:Hirudins; D020033:Protein Isoforms; D011994:Recombinant Proteins; C027539:fibrinopeptides gamma; D014443:Tyrosine; D005340:Fibrinogen; D006493:Heparin; D004247:DNA; D013917:Thrombin