Delineation of the Site of Action of an Antistaphylococcal α-Globulin

S ummary . The isolation of an antibacterial α-globulin from the sera of humans as well as selected animal species has been reported. While antibacterial agent (ABA) reduced the respiration of intact cells by 55%, the anti-respiratory effect was increased to 67% and 85% for spheroplasts and L-forms, respectively. Studies indicated that neither cell wall nor peptidoglycan could absorb ABA quickly enough to inhibit its membrane damaging effects. Although the ribitol teichoic acid-free mutant Staphylococcus aureus H52A5 was not susceptible to ABA, the lack of ribitol teichoic acid may have altered structurally the cell wall so that ABA access to the cell membrane was precluded. The activity of ABA was neutralized by prior exposure of staphylococci to exogenous coagulase, presumably by masking unknown receptor sites for ABA on the cell surface. In our studies with cell wall deficient organisms, we could not demonstrate coagulase reversal of ABA activity.