Denome S A, Oldfield C, Nash L J, Young K D
Department of Microbiology and Immunology, University of North Dakota School of Medicine, Grand Forks 58202.
J Bacteriol. 1994 Nov;176(21):6707-16. doi: 10.1128/jb.176.21.6707-6716.1994.
Rhodococcus sp. strain IGTS8 possesses an enzymatic pathway that can remove covalently bound sulfur from dibenzothiophene (DBT) without breaking carbon-carbon bonds. The DNA sequence of a 4.0-kb BstBI-BsiWI fragment that carries the genes for this pathway was determined. Frameshift and deletion mutations established that three open reading frames were required for DBT desulfurization, and the genes were designated soxABC (for sulfur oxidation). Each sox gene was subcloned independently and expressed in Escherichia coli MZ1 under control of the inducible lambda pL promoter with a lambda cII ribosomal binding site. SoxC is an approximately 45-kDa protein that oxidizes DBT to DBT-5,5'-dioxide. SoxA is an approximately 50-kDa protein responsible for metabolizing DBT-5,5'-dioxide to an unidentified intermediate. SoxB is an approximately 40-kDa protein that, together with the SoxA protein, completes the desulfurization of DBT-5,5'-dioxide to 2-hydroxybiphenyl. Protein sequence comparisons revealed that the predicted SoxC protein is similar to members of the acyl coenzyme A dehydrogenase family but that the SoxA and SoxB proteins have no significant identities to other known proteins. The sox genes are plasmidborne and appear to be expressed as an operon in Rhodococcus sp. strain IGTS8 and in E. coli.
红球菌属IGTS8菌株拥有一条酶促途径，该途径能够从二苯并噻吩（DBT）中去除共价结合的硫，而不破坏碳-碳键。测定了携带该途径基因的一个4.0 kb BstBI - BsiWI片段的DNA序列。移码突变和缺失突变表明，DBT脱硫需要三个开放阅读框，这些基因被命名为soxABC（用于硫氧化）。每个sox基因都被独立亚克隆，并在具有λ cII核糖体结合位点的可诱导λ pL启动子控制下在大肠杆菌MZ1中表达。SoxC是一种约45 kDa的蛋白质，它将DBT氧化为DBT - 5,5'-二氧化物。SoxA是一种约50 kDa的蛋白质，负责将DBT - 5,5'-二氧化物代谢为一种未知中间体。SoxB是一种约40 kDa的蛋白质，它与SoxA蛋白一起，将DBT - 5,5'-二氧化物完全脱硫为2 - 羟基联苯。蛋白质序列比较显示，预测的SoxC蛋白与酰基辅酶A脱氢酶家族成员相似，但SoxA和SoxB蛋白与其他已知蛋白质没有显著的同源性。sox基因是质粒携带的，并且在红球菌属IGTS8菌株和大肠杆菌中似乎作为一个操纵子表达。
