Tan H M, Tang H Y, Joannou C L, Abdel-Wahab N H, Mason J R
Department of Microbiology, National University of Singapore.
Gene. 1993 Aug 16;130(1):33-9. doi: 10.1016/0378-1119(93)90343-2.
Benzene dioxygenase, catalyzing the oxidation of benzene to cis-1,2-dihydroxy-cyclohexa-3,5-diene, comprises four polypeptides that are encoded by plasmid pHMT112 of Pseudomonas putida ML2. In this study, the nucleotide (nt) sequences of four genes encoding this enzyme (bedC1C2BA) were determined, and the amino acid (aa) sequences were deduced. The sequence showed significant homology with the chromosomally encoded benzene dioxygenase and toluene dioxygenase genes (73-77% for nt and 83-99% for aa), but not the plasmid-encoded naphthalene dioxygenase genes (20-26% for nt and 32-36% for aa). A conserved motif (Cys-Xaa-His-15-to-17 aa-Cys-Xaa2-His, where Xaa is any aa), proposed to bind the Rieske-type [2Fe-2S] cluster, was identified in the deduced aa sequence of the iron-sulfur proteins. Three regions were also identified in the flavoprotein which are likely to be involved in FAD and NAD+ binding. The gene order of bedC1C2BA is consistent with most ring-hydroxylating dioxygenases isolated from Pseudomonas. However, the G+C content of 47% is in contrast to the high G+C content of the Pseudomonas chromosome (63%) and other Pseudomonas plasmids (57%), and with its unique codon usage preference this suggests that bedC1C2BA originated from a host derived from a different genus.
苯双加氧酶可催化苯氧化为顺式-1,2-二羟基-环己-3,5-二烯，它由恶臭假单胞菌ML2的质粒pHMT112编码的四种多肽组成。在本研究中，测定了编码该酶的四个基因（bedC1C2BA）的核苷酸（nt）序列，并推导了氨基酸（aa）序列。该序列与染色体编码的苯双加氧酶和甲苯双加氧酶基因具有显著同源性（核苷酸同源性为73 - 77%，氨基酸同源性为83 - 99%），但与质粒编码的萘双加氧酶基因不同源（核苷酸同源性为20 - 26%，氨基酸同源性为32 - 36%）。在铁硫蛋白的推导氨基酸序列中鉴定出一个保守基序（Cys-Xaa-His-15至17个氨基酸-Cys-Xaa2-His，其中Xaa为任意氨基酸），该基序被认为可结合Rieske型[2Fe-2S]簇。在黄素蛋白中还鉴定出三个可能参与FAD和NAD⁺结合的区域。bedC1C2BA的基因顺序与从假单胞菌中分离出的大多数环羟基化双加氧酶一致。然而，其47%的G+C含量与假单胞菌染色体的高G+C含量（63%）和其他假单胞菌质粒（57%）形成对比，并且由于其独特的密码子使用偏好，这表明bedC1C2BA起源于不同属的宿主。
