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        Our laboratory studies several blood plasma proteins that interact with components of the extracellular matrix to regulate blood coagulation, inflammation and wound healing.

        The major emphasis of the laboratory has been to elucidate the mechanism of action of a plasma protein termed heparin cofactor II (HCII).  HCII inhibits thrombin, the final protease of the blood coagulation cascade.  Inhibition occurs when thrombin attacks the Leu444-Ser445 bond in HCII leading to formation of a covalent complex between the two proteins.  Sulfated polysaccharides (including heparan sulfate and dermatan sulfate) on the surface of fibroblasts and certain other cells bind HCII and stimulate its activity ~1000-fold, a process that may localize the site of action of HCII in vivo.  Specific oligosaccharide sequences in dermatan sulfate chains are required to stimulate HCII.  We are determining the structures of these oligosaccharides using a variety of chemical and enzymatic degradation techniques.  In addition, we have cloned the cDNA and the gene for human and murine HCII and have expressed the recombinant protein in E. coli.  We are studying the protease- and oligosaccharide-binding domains of HCII by analysis of natural point mutations in the HCII gene, by site-directed mutagenesis of the cDNA, and by computer-assisted modelling.  Immunohistochemical methods and targeted gene disruption are being used to investigate the physiology of HCII in the mouse.

Model depicting residues 105-477 of human heparin cofactor II

Residues that are identical in mammals, birds, and amphibians are white.  Residues that differ among species are black.  The "front" orientation displays the highly conserved reactive site loop (residues 439-447) and the glycosaminoglycan-binding site (residues 173, 184, 185, 189, 192, and 193).

From Colwell NS & Tollefsen DM: Thromb Haemost 1998 Nov;80(5):784-90

Protein Chemistry
Gene, Biosynthesis, and Metabolism
Interaction with Heparin and Dermatan Sulfate
Stimulation by Glycosaminoglycans
Physiologic Function
Selected References

Coagulation in vitro
        "Intrinsic" and "extrinsic" coagulation pathways
        Identification of distinct coagulation factors
        Sequence of coagulation reactions
Coagulation in vivo
        Exposure of plasma to tissue factor initiates coagulation
        Coagulation can be initiated via the "intrinsic" pathway in vitro
        Concentrations of coagulation factors required for normal hemostasis
Biochemistry of coagulation
        Structure of coagulation protease zymogens
        Non-enzymatic protein cofactors
        Prothrombin activation
        Fibrinogen
        Factor XIII
        Amplification and localization of coagulation reactions