Selected Publications

Plasminogen is an inactive enzyme precursor that is present at high concentration in circulating blood plasma. Upon activation by highly specific limited proteases (urokinase, tissue plasminogen activator), or by nonproteolytic activators of bacterial origin (streptokinase), it is transformed into the protease plasmin, an enzyme that is particularly effective in digesting fibrinogen and fibrin. Since fibrin forms the matrix of blood clots, the activation of plasminogen is the reaction that is exploited clinically to dissolve intravascular clots such as those responsible for heart attack, stroke, and vascular thrombosis generally.

The laboratory's current work is committed to elucidating the basis of specificity in plasminogen activation by urokinase and streptokinase, using a structure-activity analysis employing protein engineering and X-ray crystallography. For this purpose, microplasminogen, consisting only of the proenzyme domain of plasminogen, has been subjected to site-directed mutagenesis to identify specificity determinants of the interactions with the two activators. Concurrently, in collaboration with Dr. D. Ringe of Brandeis University, microplasminogen has been crystallized and its structure is being analyzed. Analysis of a series of mutant structures is expected to yield insights into the mechanisms of proenzyme activation generally, and to explain the remarkable specificity of urokinase and streptokinase. The interaction of streptokinase and plasminogen is of particular interest because it yields a 1:1 complex in which an enzymatic active site is formed reversibly in plasminogen in the absence of any limited proteolytic cleavage of the zymogen; understanding the mechanism of this active site formation could lead to the design of drugs which would permit the controlled activation of plasminogen in vivo, thereby reducing and perhaps eliminating the risk of intravascular clotting.

Selected Publications

Wang, J., Brdar, B. and Reich, E. (1995). Structure and function of microplasminogen: I. Methionine shuffling, chemical proteolysis, and proenzyme activation. Protein Sci. 4. 1758-1767.

Wang, J. and Reich, E. (1995). Structure and function of microplasminogen: II. Determinants of activation by urokinase and by the bacterial activator streptokinase Protein Sci. 4: 1768-1779.

Wang, J., de los Santos, T., and Reich, E. (1996). Structure and function of microplasminogen: III. Reconstitution of microplasminogen and microplasmin from fragments. Protein Sci. (Submitted for publication)