Department of Chemistry, University of Massachusetts Boston, Boston, MA, 02125, USA.
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA.
Biochem Biophys Res Commun. 2020 Jan 29;522(1):107-112. doi: 10.1016/j.bbrc.2019.11.008. Epub 2019 Nov 18.
Methyl sulfur compounds are a rich source of environmental sulfur for microorganisms, but their use requires redox systems. The bacterial sfn and msu operons contain two-component flavin-dependent monooxygenases for dimethylsulfone (DMSO) assimilation: SfnG converts DMSO to methanesulfinate (MSI), and MsuD converts methanesulfonate (MS) to sulfite. However, the enzymatic oxidation of MSI to MS has not been demonstrated, and the function of the last enzyme of the msu operon (MsuC) is unresolved. We employed crystallographic and biochemical studies to identify the function of MsuC from Pseudomonas fluorescens. The crystal structure of MsuC adopts the acyl-CoA dehydrogenase fold with putative binding sites for flavin and MSI, and functional assays of MsuC in the presence of its oxidoreductase MsuE, FMN, and NADH confirm the enzymatic generation of MS. These studies reveal that MsuC converts MSI to MS in sulfite biosynthesis from DMSO.
甲基硫化合物是微生物环境硫的丰富来源，但它们的使用需要氧化还原系统。细菌 sfn 和 msu 操纵子包含两种组分黄素依赖的单加氧酶，用于二甲基砜（DMSO）同化：SfnG 将 DMSO 转化为甲烷亚磺酸盐（MSI），而 MsuD 将甲烷磺酸盐（MS）转化为亚硫酸盐。然而，MSI 到 MS 的酶促氧化尚未得到证明，并且 msu 操纵子的最后一个酶（MsuC）的功能尚未解决。我们采用晶体学和生物化学研究来鉴定荧光假单胞菌中 MsuC 的功能。MsuC 的晶体结构采用酰基辅酶 A 脱氢酶折叠，具有黄素和 MSI 的可能结合位点，并且在其氧化还原酶 MsuE、FMN 和 NADH 的存在下进行 MsuC 的功能测定证实了 MS 的酶促生成。这些研究表明，MsuC 在 DMSO 合成亚硫酸盐的过程中，将 MSI 转化为 MS。
