ANTICOAGULANT PROTEIN STRUCTURE AND FUNCTION

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Diffraction quality and experimental plan: Test images of each of our crystals indicate crisp spots with low mosaicity and no indication of twinning. We calculate the following sweeps for 100 % completeness: crystal 1: 94 deg crystal 2: 116 deg crystal 3: 122 deg. Importance: Crystal 1 is of a unique calcium dependent antibody with metal binding sites within the antibody itself. However, modelling studies indicate that our calcium binding sites and the conformational effects of metal binding are quite unique compared to the only other structure of a calcium dependent antibody reported by Hendrickson`s group (Zhou et al. PNAS 102:14575 (2005)). This structure should provide information on both the metal and antigen binding ability of this monoclonal. Crystal 2 is the first look at this important enzyme-cofactor complex with an uninhibited active site. As such we expect to understand more about the allosteric effect that thrombomodulin has on thrombin`s active site as it switches thrombin from its procoagulant activity to the anticoagulant pathway. Crystal 3 adds the kazal class inhibitor Bovine Pancreatic Trypsin Inhibitor (BPTI) to the ctystal 2 complex. This is significant because BPTI does not bind to thrombin alone and only inhibits the thrombon-thrombomodulin complex. This structure should prorvide a wealth of information about the allosteric effect of thrombomodulin and is a natural companion structure to crystal 2.