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.
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机译:已知牛中性粒细胞颗粒的提取物在体外具有显着的抗菌活性。通过简单的两步色谱程序,我们已经解析了抗菌系统的两个肽组分。它们从泛霉素中被命名为Bac-5和Bac-7,分子量分别约为5和7千道尔顿。两种细菌素中超过45%和20%的氨基酸残基分别是脯氨酸和精氨酸。其余氨基酸主要是疏水性的(异亮氨酸,亮氨酸和苯丙氨酸)。 Bac-5和Bac-7均可有效杀死大肠杆菌,鼠伤寒沙门氏菌和肺炎克雷伯菌。它们还阻止阴沟肠杆菌(MIC,25至200微克/毫升)的生长,但不抑制寻常变形杆菌,金黄色葡萄球菌和无乳链球菌(MIC,大于200微克/毫升)的生长。最后,对于铜绿假单胞菌和表皮葡萄球菌,Bac-7而不是Bac-5的MIC小于或等于200微克/毫升。通过比较体外有效杀菌浓度和嗜中性粒细胞中细菌素的估计含量(每10(6)个细胞中分别有125 ng Bac-5和Bac-7),可以合理地推断出这两种阳离子肽可能发挥了作用在宿主防御至少某些微生物中起重要作用。
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