Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2620, Ciudad Autónoma de Buenos Aires, Argentina; IQUIBICEN-UBA/CONICET, Intendente Güiraldes 2620, Ciudad Autónoma de Buenos Aires, Argentina.
Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes 2620, Ciudad Autónoma de Buenos Aires, Argentina.
Biochem Biophys Res Commun. 2018 Mar 29;498(2):288-295. doi: 10.1016/j.bbrc.2017.08.119. Epub 2017 Aug 30.
Tuberculosis (TB) is a chronic disease caused by the bacillus Mycobacterium tuberculosis(Mtb) and remains a leading cause of mortality worldwide. The bacteria has an external wall which protects it from being killed, and the enzymes involved in the biosynthesis of the cell wall components have been proposed as promising targets for future drug development efforts. Cyclopropane Mycolic Acid Synthases (CMAS) constitute a group of ten homologous enzymes which belong to the mycolic acid biosynthesis pathway. These enzymes have S-adenosyl-l-methionine (SAM) dependent methyltransferase activity with a peculiarity, each one of them has strong substrate selectivity and reaction specificity, being able to produce among other things cyclopropanes or methyl-alcohol groups from the lipid olefin group. How each CMAS processes its substrate and how the specificity and selectivity are encoded in the protein sequence and structure, is still unclear. In this work, by using a combination of modeling tools, including comparative modeling, docking, all-atom MD and QM/MM methodologies we studied in detail the reaction mechanism of cmaA2, mmaA4, and mmaA1 CMAS and described the molecular determinants that lead to different products. We have modeled the protein-substrate complex structure and determined the free energy pathway for the reaction. The combination of modeling tools at different levels of complexity allows having a complete picture of the CMAS structure-activity relationship.
结核病（TB）是一种由结核分枝杆菌（Mtb）引起的慢性疾病，仍然是全球死亡的主要原因。这种细菌有一个外部细胞壁，可以保护它免受伤害，参与细胞壁成分生物合成的酶已被提议作为未来药物开发努力的有希望的目标。环丙烷分枝酸合成酶（CMAS）是一组十个同源酶，属于分枝酸生物合成途径。这些酶具有 S-腺苷甲硫氨酸（SAM）依赖性甲基转移酶活性，具有一个特殊性，它们中的每一个都具有很强的底物选择性和反应特异性，能够从脂质烯烃基团中产生环丙烷或甲醇基团等物质。每个 CMAS 如何处理其底物，以及特异性和选择性如何在蛋白质序列和结构中编码，仍然不清楚。在这项工作中，我们使用了一系列建模工具，包括比较建模、对接、全原子 MD 和 QM/MM 方法，详细研究了 cmaA2、mmaA4 和 mmaA1 CMAS 的反应机制，并描述了导致不同产物的分子决定因素。我们已经构建了蛋白质-底物复合物的结构，并确定了反应的自由能途径。不同复杂程度的建模工具的结合可以全面了解 CMAS 的结构-活性关系。
