PDF(Pubmed)
Abstract：
A heterodisulfide reductase-like complex (sHdr) and novel lipoate-binding proteins (LbpAs) are central players of a wide-spread pathway of dissimilatory sulfur oxidation. Bioinformatic analysis demonstrate that the cytoplasmic sHdr-LbpA systems are always accompanied by sets of sulfur transferases (DsrE proteins, TusA, and rhodaneses). The exact composition of these sets may vary depending on the organism and sHdr system type. To enable generalizations, we studied model sulfur oxidizers from distant bacterial phyla, that is, Aquificota and Pseudomonadota. DsrE3C of the chemoorganotrophic Alphaproteobacterium Hyphomicrobium denitrificans and DsrE3B from the Gammaproteobacteria Thioalkalivibrio sp. K90mix, an obligate chemolithotroph, and Thiorhodospira sibirica, an obligate photolithotroph, are homotrimers that donate sulfur to TusA. Additionally, the hyphomicrobial rhodanese-like protein Rhd442 exchanges sulfur with both TusA and DsrE3C. The latter is essential for sulfur oxidation in Hm. denitrificans. TusA from Aquifex aeolicus (AqTusA) interacts physiologically with AqDsrE, AqLbpA, and AqsHdr proteins. This is particularly significant as it establishes a direct link between sulfur transferases and the sHdr-LbpA complex that oxidizes sulfane sulfur to sulfite. In vivo, it is unlikely that there is a strict unidirectional transfer between the sulfur-binding enzymes studied. Rather, the sulfur transferases form a network, each with a pool of bound sulfur. Sulfur flux can then be shifted in one direction or the other depending on metabolic requirements. A single pair of sulfur-binding proteins with a preferred transfer direction, such as a DsrE3-type protein towards TusA, may be sufficient to push sulfur into the sink where it is further metabolized or needed.
摘要：
异二硫还原酶样复合物（sHdr）和新型硫辛酸结合蛋白（LbpAs）是广泛的异化硫氧化途径的核心参与者。生物信息学分析表明，细胞质sHdr-LbpA系统总是伴随着硫转移酶（DsrE蛋白，Tusa,和罗丹塞斯）。这些组的确切组成可以根据生物体和sHdr系统类型而变化。要启用概括，我们研究了遥远细菌门的硫氧化剂模型，也就是说,Aquificota和Pseudomonadota。化学有机营养的α-变形杆菌脱氮微生物的DsrE3C和来自γ-变形杆菌的DsrE3B。K90mix,一种专性化学营养，和西比利卡西奥霍多螺旋体，一个强制性的光刻系统，是向图萨捐赠硫的同质三聚体。此外,抗菌类罗丹蛋白Rhd442与TusA和DsrE3C交换硫。后者对于Hm中的硫氧化是必需的。dennitrificans.来自Aquifexaeolicus（AqTusA）的TusA与AqDsrE在生理上相互作用，AqLbpA,和AqsHdr蛋白。这是特别重要的,因为它建立了硫转移酶和将硫烷硫氧化为亚硫酸盐的sHdr-LbpA络合物之间的直接联系。在体内,研究的硫结合酶之间不太可能存在严格的单向转移。相反，硫转移酶形成一个网络，每个都有一池结合的硫磺。然后可以根据代谢要求在一个方向或另一个方向上移动硫通量。一对具有首选转移方向的硫结合蛋白，例如针对TusA的DsrE3型蛋白质，可能足以将硫推入进一步代谢或需要的汇中。
