Abstract
Six antimicrobial peptides, corresponding to the family of "lysosomal cationic proteins" described previously by Zeya and Spitznagel (H. I. Zeya and J. K. Spitznagel, J. Bacteriol. 91:750-754, 1966; H. I. Zeya and J. K. Spitznagel, J. Bacteriol. 91:755-762, 1966), were purified from rabbit peritoneal granulocytes by preparative acrylamide gel electrophoresis and reversed-phase high-pressure liquid chromatography. Each of the peptides was of low molecular weight (ca. 4,000) as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The two most cationic peptides, NP-1 and NP-2, were active against a broad spectrum of gram-positive and gram-negative bacteria. The remaining four peptides, NP-3A, NP-3B, NP-4, and NP-5, had more selective antibacterial activity. None of the peptides was active against Bordetella bronchiseptica, a common pathogen of domestic rabbits. Antibacterial activity was best expressed at near neutral pH under conditions of low ionic strength.