The long term goal of this project is to understand serpin (serine protease inhibitor) structure/function relationships by studying naturally occurring and in vitro generated serpin mutants. Improved understanding of serpin structure/function principles will lead to more effective treatment for thrombosis, bleeding, permeability and pulmonary disorders associated with serpin/protease imbalances.
Specific Aim 1 is to determine why perturbations of the P12 region change a serpin from an inhibitor to a substrate. The P12 region is located on the amino terminal side of the reactive center. Analysis of naturally occurring serpin mutants indicates that the P12 region is involved in determining whether a serpin is an inhibitor or a substrate for its target protease(s). A model for the role of the P12 region in determining serpin inhibitor/substrate status is proposed and will be tested by studying the interactions of normal serpins and P12 region mutants with proteases.
Specific Aim 2 is to determine why integrity of the ATIII P11' region is required to obtain normal circulating levels of a serpin. The P11' region is located on the carboxy terminal side of the reactive center. Naturally occurring serpin mutants with lesions in the P11' region are present at extremely reduced levels in the circulation, suggesting that it is important for determining intracellular degradation, secretion or clearance rates. These parameters will be studied in cells expressing normal serpins and Pll' region mutants in order to elucidate the role the Pll' region plays in determining circulating serpin levels.
Specific Aim 3 is to elucidate the structural basis of antithrombin III heparin cofactor activity. A model for ATIII heparin cofactor activity is proposed and will be tested by making antithrombin mutants with defined structural abnormalities and studying their functional properties. A further test of the model will involve trying to transfer the heparin cofactor property of antithrombin III to another serpin, such as alpha 1-antitrypsin.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Hematology Subcommittee 2 (HEM)
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Temple University
Schools of Medicine
United States
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Schedin-Weiss, Sophia; Desai, Umesh R; Bock, Susan C et al. (2004) Roles of N-terminal region residues Lys11, Arg13, and Arg24 of antithrombin in heparin recognition and in promotion and stabilization of the heparin-induced conformational change. Biochemistry 43:675-83
Jairajpuri, Mohamad Aman; Lu, Aiqin; Desai, Umesh et al. (2003) Antithrombin III phenylalanines 122 and 121 contribute to its high affinity for heparin and its conformational activation. J Biol Chem 278:15941-50
Schedin-Weiss, Sophia; Arocas, Veronique; Bock, Susan C et al. (2002) Specificity of the basic side chains of Lys114, Lys125, and Arg129 of antithrombin in heparin binding. Biochemistry 41:12369-76
Olson, Steven T; Bjork, Ingemar; Bock, Susan C (2002) Identification of critical molecular interactions mediating heparin activation of antithrombin: implications for the design of improved heparin anticoagulants. Trends Cardiovasc Med 12:198-205
Schedin-Weiss, Sophia; Desai, Umesh R; Bock, Susan C et al. (2002) Importance of lysine 125 for heparin binding and activation of antithrombin. Biochemistry 41:4779-88
Jairajpuri, Mohamad Aman; Lu, Aiqin; Bock, Susan C (2002) Elimination of P1 arginine 393 interaction with underlying glutamic acid 255 partially activates antithrombin III for thrombin inhibition but not factor Xa inhibition. J Biol Chem 277:24460-5
Chuang, Y J; Swanson, R; Raja, S M et al. (2001) The antithrombin P1 residue is important for target proteinase specificity but not for heparin activation of the serpin. Characterization of P1 antithrombin variants with altered proteinase specificity but normal heparin activation. Biochemistry 40:6670-9
Arocas, V; Bock, S C; Raja, S et al. (2001) Lysine 114 of antithrombin is of crucial importance for the affinity and kinetics of heparin pentasaccharide binding. J Biol Chem 276:43809-17
Arocas, V; Turk, B; Bock, S C et al. (2000) The region of antithrombin interacting with full-length heparin chains outside the high-affinity pentasaccharide sequence extends to Lys136 but not to Lys139. Biochemistry 39:8512-8
Desai, U; Swanson, R; Bock, S C et al. (2000) Role of arginine 129 in heparin binding and activation of antithrombin. J Biol Chem 275:18976-84

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