BINDING OF TISSUE-TYPE PLASMINOGEN-ACTIVATOR (T-PA) TO NEISSERIA-MENINGITIDIS AND HAEMOPHILUS-INFLUENZAE

Forty-nine bacterial strains representing five; species known to inter act with human plasminogen were tested for the ability to bind the two major human plasminogen activators, t-PA and urokinase. The bacterial species tested included Haemophilus influenzae, Neisseria meningitidi s, Streptococcus pyogenes, Streptococcus equisimilis and human group G streptococci. All N. meningitidis and 11 of 14 H. influenzae strains displayed substantial binding of t-PA with values in the range of 20-4 6%. On the contrary, none of the streptococcal strains bound significa nt amounts of tPA. With urokinase no binding could be found for any of the bacterial species tested. Scatchard analysis with a selected H. i nfluenzae strain (HI23354) demonstrated 10000 receptors per bacterium for t-PA with a K-d value of about 20 nmol 1(-1). The corresponding va lues with a selected N. meningitidis strain (Mo 52) was 8500 receptors per bacterium and 70 nmol l(-1). t-PA binding could be reduced about 40% by the addition of 10 mmol l(-1) of the lysine analogue epsilon-am inocaproic acd (EACA) whereas no inhibitory effect could be demonstrat ed with arginine. Addition of 2 mu mol l(-1) of plasminogen which is e nough to occupy all bacterial sites for plasminogen did not interfere with the t-PA binding, suggesting that the receptors for t-PA and plas minogen are distinct. Using very high plasminogen concentrations howev er, t-PA binding could be reduced by about 50% possibly due to an inte raction between t-PA and plasminogen in the fluid phase. Our results d emonstrate the occurrence of a previously unknown type of bacterial re ceptor that is capable of specifically binding t-PA.