Summary
Coagulation factor XIII is a zymogen that can be activated by thrombin cleavage to
a transglutaminase that catalyses the formation of covalent crosslinks between fibrin
chains in the final stages of the blood clotting cascade. Although circulating factor-XIII
is composed of A and B subunits the catalytic activity is a property of the A subunits.
In this study we have constructed a plasmid (pKKF13A) that contains a cDNA encoding
the A subunit positioned downstream of a tac promoter. Escherichia coli containing this plasmid produce A subunit protein when grown in the presence of IPTG.
The cloned A subunit has been partially purified and characterized. Comparison with
A subunits purified from plasma showed that the cloned A subunits were of the same
size, assembled as dimers, and had the same native electrophoretic mobility. The cloned
A subunits expressed transglutaminase activity with putrescine, dansylcadaverine and
casein as substrates, and were able to crosslink fibrin in clots formed from A subunit
deficient plasma. These studies have demonstrated that functional recombinant factor
XIII A subunit can be produced in E. coli and suggest that recombinant factor XIII can potentially provide a safe and inexhaustible
supply for therapeutic use.