title: Transmission of conformational change from the heparin binding site to the reactive center of antithrombin.
abstract: Heparin greatly increases the rates at which antithrombin inhibits target proteinases. An important part of this rate acceleration is a heparin-induced conformational change in antithrombin. To answer the question of whether or not this change is transmitted to the reactive center, we have prepared a recombinant P1 mutant of antithrombin, R393C, labeled the cysteine with nitrobenzofuran (NBD) fluorophore, and examined the perturbation of NBD fluorescence intensity as a function of bound sulfated oligosaccharide. Two high-affinity heparins, low-affinity heparin, and dextran sulfate were used. We found (i) that binding to antithrombin of all these oligosaccharides resulted in transmission of conformational change to P1 in the reactive center, (ii) that these oligosaccharides all gave enhancements of the rate of inhibition of factor Xa beyond any contribution from surface approximation, and (iii) that the degree of perturbation of P1 correlated with the enhancement of the rate of factor Xa inhibition that was not due to surface approximation.
authors.affiliation: Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
authors.forename: P G
authors.initials: PG
authors.lastname: Gettins
authors.forename: B
authors.initials: B
authors.lastname: Fan
authors.forename: B C
authors.initials: BC
authors.lastname: Crews
authors.forename: I V
authors.initials: IV
authors.lastname: Turko
authors.forename: S T
authors.initials: ST
authors.lastname: Olson
authors.forename: V J
authors.initials: VJ
authors.lastname: Streusand
mesh_terms: D000991:Antithrombins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D016264:Dextran Sulfate / Q000378:metabolism / Q000494:pharmacology; D006493:Heparin / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016376:Oligonucleotides, Antisense; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D000991:Antithrombins; D016376:Oligonucleotides, Antisense; D011994:Recombinant Proteins; D006493:Heparin; D016264:Dextran Sulfate