MANIPULATION OF THE MEMBRANE-BINDING SITE OF VITAMIN-K-DEPENDENT PROTEINS - ENHANCED BIOLOGICAL FUNCTION OF HUMAN FACTOR-VII

Recent studies suggested that modification of the membrane contact sit e of vitamin K-dependent proteins may enhance the membrane affinity an d function of members of this protein family. The properties of a fact or VII mutant, factor VII-Q10E32, relative to wild-type factor VII (VI I, containing P10K32), have been compared. Membrane affinity of VII-Q1 0E32 was about 20-fold higher than that of wild-type factor VII. The r ate of autoactivation VIII-Q10E32 with soluble tissue factor was 100-f old faster than wild-type VII and its rate of activation by factor Xa was 30 times greater than that of wild-type factor VII, When combined with soluble tissue factor and phospholipid, activated factor VII-Q10E 32 displayed increased activation of factor X, Its coagulant activity was enhanced in all types of plasma and with all sources of tissue fac tor tested, This difference in activity (maximum 50-fold) was greatest when coagulation conditions were minimal, such as limiting levels of tissue factor and/or phospholipid, Because of its enhanced activity, f actor VII-Q10E32 and its derivatives may provide important reagents fo r research and may be more effective in treatment of bleeding and/or c lotting disorders.