School of Biological Sciences, University of East Anglia, Norwich, United Kingdom.
PLoS One. 2012;7(4):e35947. doi: 10.1371/journal.pone.0035947. Epub 2012 Apr 26.
The Escherichia coli YhdH polypeptide is in the MDR012 sub-group of medium chain reductase/dehydrogenases, but its biological function was unknown and no phenotypes of YhdH(-) mutants had been described. We found that an E. coli strain with an insertional mutation in yhdH was hyper-sensitive to inhibitory effects of acrylate, and, to a lesser extent, to those of 3-hydroxypropionate. Close homologues of YhdH occur in many Bacterial taxa and at least two animals. The acrylate sensitivity of YhdH(-) mutants was corrected by the corresponding, cloned homologues from several bacteria. One such homologue is acuI, which has a role in acrylate degradation in marine bacteria that catabolise dimethylsulfoniopropionate (DMSP) an abundant anti-stress compound made by marine phytoplankton. The acuI genes of such bacteria are often linked to ddd genes that encode enzymes that cleave DMSP into acrylate plus dimethyl sulfide (DMS), even though these are in different polypeptide families, in unrelated bacteria. Furthermore, most strains of Roseobacters, a clade of abundant marine bacteria, cleave DMSP into acrylate plus DMS, and can also demethylate it, using DMSP demethylase. In most Roseobacters, the corresponding gene, dmdA, lies immediately upstream of acuI and in the model Roseobacter strain Ruegeria pomeroyi DSS-3, dmdA-acuI were co-regulated in response to the co-inducer, acrylate. These observations, together with findings by others that AcuI has acryloyl-CoA reductase activity, lead us to suggest that YdhH/AcuI enzymes protect cells against damaging effects of intracellular acryloyl-CoA, formed endogenously, and/or via catabolising exogenous acrylate. To provide "added protection" for bacteria that form acrylate from DMSP, acuI was recruited into clusters of genes involved in this conversion and, in the case of acuI and dmdA in the Roseobacters, their co-expression may underpin an interaction between the two routes of DMSP catabolism, whereby the acrylate product of DMSP lyases is a co-inducer for the demethylation pathway.
大肠杆菌 YhdH 多肽属于 MDR012 亚群中的中链还原酶/脱氢酶，但它的生物学功能未知，也没有描述 YhdH(-)突变体的表型。我们发现，带有插入突变的 yhdH 的大肠杆菌菌株对丙烯酸盐的抑制作用非常敏感，并且对 3-羟基丙酸的抑制作用也较小。 YhdH 的密切同源物存在于许多细菌分类群中，并且至少存在于两种动物中。 YhdH(-)突变体的丙烯酸盐敏感性可通过来自几种细菌的相应克隆同源物纠正。其中一个同源物是 acuI，它在海洋细菌中降解丙烯酸盐的作用，这些细菌可以代谢二甲亚砜丙酸盐 (DMSP)，这是一种由海洋浮游植物产生的丰富抗应激化合物。这些细菌的 acuI 基因通常与编码将 DMSP 切割成丙烯酸盐加二甲基硫醚 (DMS)的 ddd 基因相连，尽管这些基因属于不同的多肽家族，而且存在于不同的细菌中。此外，Roseobacters 的大多数菌株是丰富的海洋细菌的一个分支，它们可以将 DMSP 切割成丙烯酸盐加 DMS，并且还可以使用 DMSP 脱甲基酶将其脱甲基。在大多数 Roseobacters 中，相应的基因 dmdA 位于 acuI 的上游，在模型 Roseobacter 菌株 Ruegeria pomeroyi DSS-3 中，dmdA-acuI 是在共诱导剂丙烯酸盐的作用下共同调控的。这些观察结果，以及其他人的发现，即 AcuI 具有丙烯酰辅酶 A 还原酶活性，使我们认为 YdhH/AcuI 酶可以保护细胞免受内源形成的细胞内丙烯酰辅酶 A 以及/或者通过代谢外源性丙烯酸盐的有害影响。为了为从 DMSP 形成丙烯酸盐的细菌提供“附加保护”， acuI 被招募到参与这种转化的基因簇中，并且在 Roseobacters 中的 acuI 和 dmdA 的情况下，它们的共表达可能是 DMSP 分解代谢两条途径之间相互作用的基础，其中 DMSP 裂解酶的丙烯酸盐产物是脱甲基途径的共诱导物。
