STAPHYLOCIDAL ACTION OF THROMBIN-INDUCED PLATELET MICROBICIDAL PROTEIN IS NOT SOLELY DEPENDENT ON TRANSMEMBRANE POTENTIAL

Thrombin-induced platelet microbicidal protein (tPMP) is a small, cati onic, antimicrobial peptide released from rabbit platelets when stimul ated with thrombin. We studied the relationship between staphylococcal transmembrane potential (Delta psi) and tPMP staphylocidal activity. A genetically related pair of Staphylococcus aureus strains, 6850 and JB1, which differ in Delta psi generation (-143 and -97 mV, respective ly) were used. Mutant JB-1 was substantially less susceptible to tPMP than the parental strain, 6850. Menadione supplementation, which norma lized the Delta psi of strain JB-1, did not restore JB-1 tPMP suscepti bility. These findings suggest that the staphylocidal activities of tP MP require factors other than or in addition to an intact Delta psi.