Purification, composition, and activity of two bactenecins, antibacterial peptides of bovine neutrophils.
Extracts of granules of bovine neutrophils are known to exhibit a marked antibacterial activity in vitro. By a simple, two-step chromatographic procedure, we have resolved two peptide components of the antibacterial system. They were named Bac-5 and Bac-7 from the general term bactenecin and had molecular masses of about 5 and 7 kilodaltons, respectively. Over 45 and 20% of the amino acid residues in the two bactenecins are proline and arginine, respectively. The remaining amino acids are mainly hydrophobic (isoleucine, leucine, and phenylalanine). Both Bac-5 and Bac-7 efficiently kill Escherichia coli, Salmonella typhimurium, and Klebsiella pneumoniae. They also arrest the growth of Enterobacter cloacae (MICs, 25 to 200 micrograms/ml) but not of Proteus vulgaris, Staphylococcus aureus, and Streptococcus agalactiae (MIC, greater than 200 micrograms/ml). Finally, Bac-7 but not Bac-5 has MICs of less than or equal to 200 micrograms/ml for Pseudomonas aeruginosa and Staphylococcus epidermidis. From the comparison between the efficient bactericidal concentrations in vitro and the estimated content of bactenecins in neutrophils (125 ng of Bac-5 and Bac-7 each per 10(6) cells), it is reasonable to conclude that the two cationic peptides may exert a major role in host defense against at least some microorganisms.
Department of Biochemistry, Biophysics, and Macromolecular Chemistry, University of Trieste, Italy.
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R
Gennaro
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B
Skerlavaj
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D
Romeo
D000596:Amino Acids / Q000302:isolation & purification; D000818:Animals; D000890:Anti-Infective Agents / Q000097:blood / Q000302:isolation & purification* / Q000494:pharmacology; D001770:Blood Bactericidal Activity; D002417:Cattle; D003594:Cytoplasmic Granules / Q000032:analysis; D008826:Microbial Sensitivity Tests; D009504:Neutrophils / Q000032:analysis*; D010456:Peptides, Cyclic / Q000097:blood / Q000302:isolation & purification* / Q000494:pharmacology
D000596:Amino Acids; D000890:Anti-Infective Agents; D010456:Peptides, Cyclic; C056454:bactenecin