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人病原体百日咳博德特氏菌的 MurG 糖基转移酶为肽聚糖生物合成的细胞质步骤提供了一个寡聚支架。

The MurG glycosyltransferase provides an oligomeric scaffold for the cytoplasmic steps of peptidoglycan biosynthesis in the human pathogen Bordetella pertussis.

机构信息

Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), F- 38000, Grenoble, France.

Brazilian Biosciences National Laboratory (LNBio), CNPEM, Campinas, 13084-971, São Paulo, Brazil.

出版信息

Sci Rep. 2019 Mar 15;9(1):4656. doi: 10.1038/s41598-019-40966-z.

Abstract

Peptidoglycan is a major component of the bacterial cell wall and thus a major determinant of cell shape. Its biosynthesis is initiated by several sequential reactions catalyzed by cytoplasmic Mur enzymes. Mur ligases (MurC, -D, -E, and -F) are essential for bacteria, metabolize molecules not present in eukaryotes, and are structurally and biochemically tractable. However, although many Mur inhibitors have been developed, few have shown promising antibacterial activity, prompting the hypothesis that within the cytoplasm, Mur enzymes could exist as a complex whose architecture limits access of small molecules to their active sites. This suggestion is supported by the observation that in many bacteria, mur genes are present in a single operon, and pairs of these genes often are fused to generate a single polypeptide. Here, we explored this genetic arrangement in the human pathogen Bordetella pertussis and show that MurE and MurF are expressed as a single, bifunctional protein. EM, small angle X-ray scattering (SAXS), and analytical centrifugation (AUC) revealed that the MurE-MurF fusion displays an elongated, flexible structure that can dimerize. Moreover, MurE-MurF interacted with the peripheral glycosyltransferase MurG, which formed discrete oligomers resembling 4- or 5-armed stars in EM images. The oligomeric structure of MurG may allow it to play a bona fide scaffolding role for a potential Mur complex, facilitating the efficient conveyance of peptidoglycan-building blocks toward the inner membrane leaflet. Our findings shed light on the structural determinants of a peptidoglycan formation complex involving Mur enzymes in bacterial cell wall formation.

摘要

肽聚糖是细菌细胞壁的主要成分,因此也是决定细胞形状的主要因素。其生物合成由细胞质 Mur 酶催化的几个连续反应启动。Mur 连接酶(MurC、-D、-E 和 -F)对细菌是必不可少的,代谢不存在于真核生物中的分子,并且在结构和生物化学上是可处理的。然而,尽管已经开发出许多 Mur 抑制剂,但很少有显示出有希望的抗菌活性,这促使人们假设在细胞质中,Mur 酶可能作为一种复合物存在,其结构限制了小分子进入其活性位点的途径。这一假设得到了以下观察结果的支持:在许多细菌中,mur 基因存在于单个操纵子中,并且这些基因的对经常融合以产生单个多肽。在这里,我们探索了人类病原体百日咳博德特氏菌中的这种遗传排列,并表明 MurE 和 MurF 作为单个双功能蛋白表达。EM、小角度 X 射线散射 (SAXS) 和分析离心 (AUC) 显示,MurE-MurF 融合体显示出伸长的、灵活的结构,可以二聚化。此外,MurE-MurF 与外周糖基转移酶 MurG 相互作用,MurG 形成类似于 EM 图像中 4 或 5 臂星的离散寡聚体。MurG 的寡聚结构可能使其能够在潜在的 Mur 复合物中发挥真正的支架作用,从而促进将肽聚糖构建块有效地输送到内膜叶。我们的发现揭示了涉及细菌细胞壁形成中 Mur 酶的肽聚糖形成复合物的结构决定因素。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/6ae3/6420597/88d81b8a0a77/41598_2019_40966_Fig1_HTML.jpg

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