Transformation of Gram-positive microorganisms with the Gram-negative broad-host-range cosmid vector pJRD215

Abstract In an in vitro direct assay with tissue-type plasminogen activator (tPA), plasminogen and the chromogenic substrate S-2251, the ability of Mycoplasma fermentans KL4 to stimulate tPA-mediated activation of plasminogen to plasmin was studied. Mycoplasma cells markedly enhanced the activation of plasminogen by tPA in a concentration-, temperature- and pH-dependent manner. Nonidet P-40 (0.01%), sonication, and freezing and thawing of the cells substantially increased the stimulatory effect of mycoplasma on tPA activity. In contrast, the activation of plasminogen by urokinase was refractory to mycoplasma cells. The mycoplasma-mediated stimulation of tPA activity was prevented by ϵ-aminocaproic acid (EACA), a lysine analogue known to block lysine-binding sites (LBS) in plasminogen and tPA. Among several Mycoplasma fermentans strains tested, incognitus strain demonstrated the highest stimulation activity. These results suggest that mycoplasma cells interact with LBS in tPA and plasminogen to enhance plasminogen activation.