Fisher R, Blumenthal T
Proc Natl Acad Sci U S A. 1982 Feb;79(4):1045-8. doi: 10.1073/pnas.79.4.1045.
Gramicidin, a peptide antibiotic produced by Bacillus brevis, inhibits initiation of transcription by RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6). We show here that the presence of gramicidin causes an increase in the rate of cleavage of the sigma subunit of Escherichia coli RNA polymerase by trypsin, although it does not alter the cleavage rate of any of the core subunits. Furthermore, whereas isolated sigma is cleaved much faster than is sigma in holoenzyme, gramicidin substantially decreases the trypsin cleavage rate of isolated sigma. Inhibition of RNA polymerase activity by gramicidin in consistent with a sigma-specific effect: the antibiotic is a strong inhibitor of transcription of T7 phage DNA, which requires sigma for activity, but it has little effect on transcription of sigma-independent templates, such as poly(dA-dT).poly)dA-dT) and calf thymus DNA. These results are discussed in light of the hypothesized role for gramicidin in the initiation of sporulation of B. brevis.
短杆菌肽是一种由短短芽孢杆菌产生的肽抗生素，它能抑制RNA聚合酶（核苷三磷酸：RNA核苷酸转移酶，EC 2.7.7.6）介导的转录起始过程。我们在此表明，短杆菌肽的存在会导致胰蛋白酶对大肠杆菌RNA聚合酶σ亚基的切割速率增加，尽管它不会改变任何核心亚基的切割速率。此外，虽然分离的σ亚基比全酶中的σ亚基被切割得快得多，但短杆菌肽会大幅降低分离的σ亚基的胰蛋白酶切割速率。短杆菌肽对RNA聚合酶活性的抑制作用与一种σ特异性效应一致：这种抗生素是T7噬菌体DNA转录的强抑制剂，T7噬菌体DNA转录需要σ亚基发挥活性，但它对不依赖σ亚基的模板（如聚（dA-dT）·聚（dA-dT）和小牛胸腺DNA）的转录影响很小。我们根据短杆菌肽在短短芽孢杆菌芽孢形成起始过程中的假设作用对这些结果进行了讨论。
