PRIMARY STRUCTURE OF MICROCIN, J25, A BACTERIALLY EXPRESSED ANTIBIOTIC

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。所列机构为中心机构，不一定是研究者机构。Microcin J25（MccJ 25）是一种21-氨基酸肽抑制剂，对革兰氏阴性菌的DNA依赖性RNA聚合酶有活性。以前，MccJ 25的结构被报道为首尾相连的环，cyclo（-G（1）GAGHVPEYF（10）VGIGTPISFY（20）G-）。在生物化学研究、质谱和NMR的基础上，我们表明这种结构是不正确的，并且该肽具有非凡的结构折叠。MccJ 25在Gly 1的α-氨基和Glu 8的γ-羧基之间含有内部内酰胺键。尾部（Tyr 9-Gly 21）穿过环（Gly 1-Glu 8），Phe 19和Tyr 20横跨环的两侧，在空间上以非共价相互作用捕获尾部，我们称之为套索尾部。这项工作发表在J Am Chem Soc.2003 Oct 15;125（41）：12475-83上，并作为2003年化学亮点之一在化学与工程新闻中报道（Chem and Eng News Dec 22，2003）。接下来，我们将尝试确定被认为是将前蛋白转化为活性抑制剂的酶的高分辨率X射线结构。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Microcin J25 (MccJ25) is a 21-amino acid peptide inhibitor active against the DNA-dependent RNA polymerase of Gram negative bacteria. Previously, the structure of MccJ25 was reported to be a head-to-tail circle, cyclo(-G(1)GAGHVPEYF(10)VGIGTPISFY(20)G-). On the basis of biochemical studies, mass spectrometry, and NMR, we show that this structure is incorrect, and that the peptide has an extraordinary structural fold. MccJ25 contains an internal lactam linkage between the alpha-amino group of Gly1 and the gamma-carboxyl of Glu8. The tail (Tyr9-Gly21) passes through the ring (Gly1-Glu8), with Phe19 and Tyr20 straddling each side of the ring, sterically trapping the tail in a noncovalent interaction we call a lassoed tail. This work was published in J Am Chem Soc. 2003 Oct 15;125(41):12475-83 and was reported in Chemical and engineering news as one of the chemistry highlights of 2003 (Chem and Eng News Dec 22, 2003). Next, we will attempt to determine the high resolution X-ray structures of the enzymes that are thought to convert the preprotein into the active inhibitor.