Mechanisms of Iron-Sulfur Dependent Reactions

铁硫依赖性反应的机制

• 批准号: 10406673
• 负责人: SQUIRE J. BOOKER
• 金额: $ 37.01万
• 依托单位: PENNSYLVANIA STATE UNIVERSITY, THE
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-04-01 至 2027-03-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10406673
• 关键词: Anabolism; Antibiotic Resistance; Antibiotics; Antifungal Agents; Architecture; Biological; Biology; Carbapenems; Carbohydrates; Carbon; Cobalamin; DNA; Enzymes; Free Radicals; Health; Human; Hybrids; Iron; Lipids; Methylation; Methyltransferase; Natural Products; Nitrogen; Oxygen; Pathway interactions; Phosphorus; Prevalence; Process; Proteins; RNA; Reaction; Resistance; Resort; S-Adenosylhomocysteine; S-Adenosylmethionine; Source; Sulfur; System; Thiostrepton; Work; anti-cancer; base; carbanion; cofactor; enzyme structure; macromolecule; methyl group; small molecule; tRNA Methyltransferases

PROJECT SUMMARY/ABSTRACT The prevalence and significance of methylation reactions in biology is well established. Methyl groups are appended to a wide array of biological molecules, including numerous small-molecule metabolites and natural products, and various macromolecules, such as proteins, DNA, RNA, carbohydrates, and lipids. In the vast majority of methylation reactions, S-adenosylmethionine (SAM) is the source of the appended methyl group. In classical methyltransferase reactions, strong nucleophiles such as oxygen, nitrogen, and sulfur attack the sp3- hybridized methyl group of SAM in a polar SN2 reaction, affording S-adenosylhomocysteine as a co-product. Carbon atoms can also be methylated by this mechanism, but only if a suitably nucleophilic carbanion can be generated. Relatively recently, it has come to light that SAM can be used to methylate inert carbon or phosphinate phosphorous atoms via pathways involving radical intermediates. These noncanonical SAM- dependent methylations are found in numerous biosynthetic pathways for antibiotic, antifungal, anticancer, and herbicidal natural products, and are catalyzed exclusively by enzymes within the radical S- adenosylmethionine superfamily. Radical SAM methylases currently consist of three classes (Class A, Class B, and Class C) based on structural architecture, cofactor requirement, and mechanism of action. Class A enzymes use a Cys dyad to catalyze methylation of sp2-hybridized carbon centers. Class B enzymes use cobalamin cofactors to catalyze methylation of both sp2- and sp3-hybridized carbon centers. Class C enzymes use two simultaneously bound molecules of SAM to methylate sp2-hybridized carbon centers. In all cases, the appended methyl group derives from a second molecule of SAM. This work will continue our efforts to understand how these radical SAM methylases work, with a particular focus on efforts to determine structures of these enzymes with bound substrates, cofactors, and intermediates. Important systems include RNA methylases that are involved in antibiotic resistance, as well as methylases that are involved in the biosynthesis of important antibiotics, such as thiostrepton A, nosiheptide, and carbapenems, the antibiotics currently of last resort.

项目概要/摘要 生物学中甲基化反应的普遍性和重要性已众所周知。甲基是 附加到广泛的生物分子，包括许多小分子代谢物和天然 产品和各种大分子，如蛋白质、DNA、RNA、碳水化合物和脂质。在广阔的 在大多数甲基化反应中，S-腺苷甲硫氨酸 (SAM) 是附加甲基的来源。在 经典的甲基转移酶反应，强亲核试剂（例如氧、氮和硫）会攻击 sp3- 在极性 SN2 反应中杂交 SAM 的甲基，产生副产物 S-腺苷高半胱氨酸。 碳原子也可以通过这种机制甲基化，但前提是可以形成适当的亲核碳负离子。 生成的。最近，人们发现 SAM 可用于甲基化惰性碳或 通过涉及自由基中间体的途径形成次膦酸磷原子。这些非规范的 SAM- 在抗生素、抗真菌、抗癌、 和除草天然产物，并且仅由自由基 S- 内的酶催化 腺苷甲硫氨酸超家族。自由基 SAM 甲基化酶目前分为三类（A 类、B 类、 C 类）基于结构体系、辅助因子要求和作用机制。 A级 酶使用 Cys 二元体催化 sp2 杂化碳中心的甲基化。 B类酶的使用 钴胺素辅因子催化 sp2 和 sp3 杂化碳中心的甲基化。 C类酶 使用两个同时结合的 SAM 分子来甲基化 sp2 杂化碳中心。在所有情况下， 附加的甲基源自 SAM 的第二个分子。这项工作我们将继续努力 了解这些激进的 SAM 甲基化酶如何工作，特别关注确定结构的努力 这些酶与结合的底物、辅因子和中间体。重要系统包括RNA 参与抗生素耐药性的甲基化酶以及参与生物合成的甲基化酶 重要的抗生素，如硫链丝菌素A、那西肽和碳青霉烯类，是目前最后的抗生素 采取。