Cloning, Sequencing, and Expression in E. Coli and B. Subtilis of a Staphylokinase Gene

Substances that activate plasminogen have recently attracted considerable attention because of their potential application as drugs in thrombolytic therapy. Staphylokinase (SAK) elaborated by many strains of S, aureus is one of the plasminogen activating substances of bacterial origin [1,2]. Unlike the mammalian plasminogen activators urokinase [3] and tissue plasminogen activator [4] it lacks detectable proteolytic activity or any other known enzymatic property [5]. Activation of plasminogen by SAK occurs rather by a stoichiometric association of the two proteins which then results in a conversion of plasminogen to plasmin. SAK shares these peculiarities with another bacterial plasminogen activator-streptokinase, which is already commercially available as a drug [6]. Extensive studies on SAK have been hampered in the past by difficulties to purify sufficient amounts of the protein from contaminating staphylococcal toxins.