Biomedical Sciences ETDs

Publication Date

8-3-1990

Abstract

Factor VII is a trace vitamin K dependent plasma glycoprotein that circulates in blood as a single-chain zymogen and plays an important role in the initiation of the extrinsic pathway of blood coagulation. Single chain factor VII is converted to two chain factor VIIa by proteolytic cleavage of a single internal peptide bond. Factor VILa in tum activates either factor IX or factor X in a reaction that requires a lipoprotein cofactor designated tissue factor. The activation of factor VII by factor IXa and factor Xa was studied on the surface of a human bladder carcinoma cell line as well as in a suspension of mixed brain phospholipids. It was found that, depending on the surface used, factor Xa was 6-18 fold more efficient at activating factor VII than factor IXa. Since there is evidence that single-chain factor VII possesses sufficient intrinsic proteolytic activity to initiate extrinsic coagulation, a site-directed mutant of recombinant factor VII, unable to undergo proteolytic activation by arginine specific serine-proteases, was produced by replacing Arg152 with a glutamic acid residue. The mutant molecule interacted with tissue factor in a manner indistinguishable from wild-type factor VII, yet possessed less than 0.01 % the clotting activity of wild-type recombinant factor VII. These results are consistent with the proposal that zymogen factor VII possesses no proteolytic activity towards factor IX or factor X. In order to define the factor VII domains involved in the binding of factor VII to tissue factor a series of synthetic factor VII peptides based on the sequence of human factor VII were produced. One peptide spanning residues 195-206 inhibited the interaction of factor VII with tissue factor as measured in a coagulation assay, a factor X activation assay, and a J82 cell binding assay.

Document Type

Thesis

Language

English

Degree Name

Biomedical Sciences

Level of Degree

Masters

Department Name

Biomedical Sciences Graduate Program

First Committee Member (Chair)

Walter Kisiel

Second Committee Member

Carolyn Mold

Third Committee Member

Abdul-Latif Kazim

Fourth Committee Member

Kenneth J. Smith

Download

Share

COinS