Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware 19716, United States.
Department of Biological Chemistry, University of Delaware , Newark, Delaware 19716, United States.
J Am Chem Soc. 2017 Oct 4;139(39):13596-13599. doi: 10.1021/jacs.7b06820. Epub 2017 Sep 26.
Bacteria have the natural ability to install protective postsynthetic modifications onto its bacterial peptidoglycan (PG), the coat woven into bacterial cell wall. Peptidoglycan O-acetyltransferase B (PatB) catalyzes the O-acetylation of PG in Gram (-) bacteria, which aids in bacterial survival, as it prevents autolysins such as lysozyme from cleaving the PG. We explored the mechanistic details of PatB's acetylation function and determined that PatB has substrate specificity for bioorthgonal short N-acetyl cysteamine (SNAc) donors. A variety of functionality including azides and alkynes were installed on tri-N-acetylglucosamine (NAG), a PG mimic, as well as PG isolated from various Gram (+) and Gram (-) bacterial species. The bioorthogonal modifications protect the isolated PG against lysozyme degradation in vitro. We further demonstrate that this postsynthetic modification of PG can be extended to use click chemistry to fluorescently label the mature PG in whole bacterial cells of Bacillus subtilis. Modifying PG postsynthetically can aid in the development of antibiotics and immune modulators by expanding the understanding of how PG is processed by lytic enzymes.
细菌具有在其细菌肽聚糖（PG）上安装保护性的后生合成修饰的天然能力，PG 是编织在细菌细胞壁中的一层物质。肽聚糖 O-乙酰基转移酶 B（PatB）催化革兰氏阴性（-）细菌中 PG 的 O-乙酰化，这有助于细菌的存活，因为它可以防止溶菌酶等自溶酶裂解 PG。我们探索了 PatB 乙酰化功能的机制细节，并确定 PatB 对生物正交的短 N-乙酰半胱氨酸（SNAc）供体具有底物特异性。各种功能包括叠氮化物和炔烃被安装在三-N-乙酰葡萄糖胺（NAG）上，这是一种 PG 模拟物，以及从各种革兰氏阳性（+）和革兰氏阴性（-）细菌物种中分离的 PG。生物正交修饰可保护分离的 PG 免受溶菌酶在体外的降解。我们进一步证明，这种 PG 的后生合成修饰可以通过点击化学进一步扩展，用于荧光标记枯草芽孢杆菌完整细菌细胞中的成熟 PG。通过扩展对 PG 如何被溶酶体酶加工的理解，对 PG 进行后生合成修饰可以帮助开发抗生素和免疫调节剂。
