Larsen O, Lien T, Birkeland N K
Department of Microbiology, University of Bergen, Norway.
Extremophiles. 1999 Jan;3(1):63-70. doi: 10.1007/s007920050100.
The genes encoding the alpha- and beta-subunits of dissimilatory sulfite reductase, dsrAB, from the hyperthermophilic archaeon Archaeoglobus profundus and the thermophilic gram-positive bacterium Desulfotomaculum thermocisternum were cloned and sequenced. The dsrAB genes are contiguous, and most probably comprise an operon also including a dsrD homolog, a conserved gene of unknown function located downstream of dsrAB in all four sulfate reducers so far sequenced. Sequence comparison confirms that dissimilatory sulfite reductase, Dsr, is a highly conserved enzyme. A phylogenetic analysis using the available Dsr sequences, including Dsr-like proteins from nonsulfate reducers, suggests a paralogous origin of the alpha- and beta-subunits. Furthermore, the Dsr from sulfate reducers forms a separate cluster, with Dsr from the bacterial sulfate reducers Desulfotomaculum thermocisternum and Desulfovibrio vulgaris branching together, next to Dsr from Archaeoglobus profundus and Archaeoglobus fulgidus. Based on an alignment with the assimilatory sulfite reductase from Escherichia coli, the amino acid residues involved in binding of sulfite, siroheme, and [Fe4S4]-clusters have been tentatively identified, which is consistent with the binding of two sirohemes and four [Fe4S4]-clusters per alpha2beta2 structure. The evolution of Dsr and the structural basis for the binding of substrate and cofactors are discussed.
对嗜热古菌深栖嗜热栖热菌和嗜热革兰氏阳性细菌嗜热栖热脱硫肠状菌中异化亚硫酸盐还原酶的α亚基和β亚基的编码基因dsrAB进行了克隆和测序。dsrAB基因是连续的，很可能构成一个操纵子，该操纵子还包括一个dsrD同源物，这是一个功能未知的保守基因，在目前已测序的所有四种硫酸盐还原菌中位于dsrAB下游。序列比较证实，异化亚硫酸盐还原酶（Dsr）是一种高度保守的酶。利用现有的Dsr序列进行系统发育分析，包括来自非硫酸盐还原菌的类Dsr蛋白，结果表明α亚基和β亚基起源于旁系同源基因。此外，硫酸盐还原菌的Dsr形成一个单独的聚类，细菌硫酸盐还原菌嗜热栖热脱硫肠状菌和普通脱硫弧菌的Dsr一起分支，紧邻深栖嗜热栖热菌和富硫嗜热栖热菌的Dsr。基于与大肠杆菌同化亚硫酸盐还原酶的比对，初步确定了参与亚硫酸盐、西罗血红素和[Fe4S4]簇结合的氨基酸残基，这与每个α2β2结构结合两个西罗血红素和四个[Fe4S4]簇一致。文中讨论了Dsr的进化以及底物和辅因子结合的结构基础。
