Facultad de Medicina, Universidad de Oviedo 33006 Oviedo, Asturias, Spain.
J Bacteriol. 2011 Feb;193(4):944-51. doi: 10.1128/JB.01058-10. Epub 2010 Dec 17.
Application of in vivo expression technology (IVET) to Yersinia ruckeri, an important fish pathogen, allowed the identification of two adjacent genes that represent a novel bacterial system involved in the uptake and degradation of l-cysteine. Analysis of the translational products of both genes showed permease domains (open reading frame 1 [ORF1]) and amino acid position identities (ORF2) with the l-cysteine desulfidase from Methanocaldococcus jannaschii, a new type of enzyme involved in the breakdown of l-cysteine. The operon was named cdsAB (cysteine desulfidase) and is found widely in anaerobic and facultative bacteria. cdsAB promoter analysis using lacZY gene fusion showed highest induction in the presence of l-cysteine. Two cdsA and cdsB mutant strains were generated. The limited toxic effect and the low utilization of l-cysteine observed in the cdsA mutant, together with radiolabeled experiments, strongly suggested that CdsA is an l-cysteine permease. Fifty percent lethal dose (LD(50)) and competence index experiments showed that both the cdsA and cdsB loci were involved in the pathogenesis of the bacteria. In conclusion, this study has shown for the first time in bacteria the existence of an l-cysteine uptake system that together with an additional l-cysteine desulfidase-encoding gene constitutes a novel operon involved in bacterial virulence.
应用体内表达技术（IVET）于鱼类病原菌迟缓爱德华氏菌，鉴定出两个相邻的基因，这两个基因代表了一个新的细菌系统，涉及 l-半胱氨酸的摄取和降解。对这两个基因的翻译产物进行分析，发现其具有与产甲烷球菌 l-半胱氨酸脱硫酶相似的通透酶结构域（开放阅读框 1 [ORF1]）和氨基酸位置同一性（ORF2），这是一种新的参与 l-半胱氨酸分解的酶。该操纵子被命名为 cdsAB（半胱氨酸脱硫酶），广泛存在于厌氧和兼性细菌中。使用 lacZY 基因融合对 cdsAB 启动子进行分析，结果表明在存在 l-半胱氨酸的情况下，诱导作用最强。生成了两个 cdsA 和 cdsB 突变株。在 cdsA 突变体中观察到有限的毒性作用和低水平的 l-半胱氨酸利用，结合放射性标记实验，强烈表明 CdsA 是 l-半胱氨酸通透酶。半数致死剂量（LD(50)）和感受态指数实验表明，cdsA 和 cdsB 基因座均参与了细菌的发病机制。总之，本研究首次在细菌中证实了 l-半胱氨酸摄取系统的存在，该系统与另外一个编码 l-半胱氨酸脱硫酶的基因一起构成了一个新的参与细菌毒力的操纵子。
