Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA.
Laboratory for Molecular Infection Medicine, Department of Molecular Biology, Umeå University, Umeå 90187, Sweden.
Cell Chem Biol. 2021 Feb 18;28(2):213-220.e4. doi: 10.1016/j.chembiol.2020.11.006. Epub 2020 Nov 24.
Transpeptidation reinforces the structure of cell-wall peptidoglycan, an extracellular heteropolymer that protects bacteria from osmotic lysis. The clinical success of transpeptidase-inhibiting β-lactam antibiotics illustrates the essentiality of these cross-linkages for cell-wall integrity, but the presence of multiple, seemingly redundant transpeptidases in many species makes it challenging to determine cross-link function. Here, we present a technique to link peptide strands by chemical rather than enzymatic reaction. We employ biocompatible click chemistry to induce triazole formation between azido- and alkynyl-d-alanine residues that are metabolically installed in the peptidoglycan of Gram-positive or Gram-negative bacteria. Synthetic triazole cross-links can be visualized using azidocoumarin-d-alanine, an amino acid derivative that undergoes fluorescent enhancement upon reaction with terminal alkynes. Cell-wall stapling protects Escherichia coli from treatment with the broad-spectrum β-lactams ampicillin and carbenicillin. Chemical control of cell-wall structure in live bacteria can provide functional insights that are orthogonal to those obtained by genetics.
转肽作用加强了细胞壁肽聚糖的结构，细胞壁肽聚糖是一种保护细菌免受渗透裂解的细胞外杂多糖。转肽酶抑制剂β-内酰胺抗生素的临床成功说明了这些交联对于细胞壁完整性的必要性，但许多物种中存在多种看似冗余的转肽酶，这使得确定交联功能具有挑战性。在这里，我们提出了一种通过化学而非酶反应连接肽链的技术。我们利用生物相容性的点击化学在代谢性地安装在革兰氏阳性或革兰氏阴性细菌的肽聚糖中的叠氮基和炔基-d-丙氨酸残基之间诱导三唑形成。使用叠氮香豆素-d-丙氨酸（一种氨基酸衍生物）可以可视化合成的三唑交联，该衍生物在与末端炔烃反应时会发生荧光增强。细胞壁订书钉可保护大肠杆菌免受广谱β-内酰胺类抗生素氨苄西林和羧苄西林的治疗。在活细菌中对细胞壁结构进行化学控制可以提供与遗传学获得的结果正交的功能见解。
