Wang Y, Moore M, Levinson H S, Silver S, Walsh C, Mahler I
Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02254.
J Bacteriol. 1989 Jan;171(1):83-92. doi: 10.1128/jb.171.1.83-92.1989.
A 13.5-kilobase HindIII fragment, bearing an intact mercury resistance (mer) operon, was isolated from chromosomal DNA of broad-spectrum mercury-resistant Bacillus sp. strain RC607 by using as a probe a clone containing the mercury reductase (merA) gene. The new clone, pYW33, expressed broad-spectrum mercury resistance both in Escherichia coli and in Bacillus subtilis, but only in B. subtilis was the mercuric reductase activity inducible. Sequencing of a 1.8-kilobase mercury hypersensitivity-producing fragment revealed four open reading frames (ORFs). ORF1 may code for a regulatory protein (MerR). ORF2 and ORF4 were associated with cellular transport function and the hypersensitivity phenotype. DNA fragments encompassing the merA and the merB genes were sequenced. The predicted Bacillus sp. strain RC607 MerA (mercuric reductase) and MerB (organomercurial lyase) were similar to those predicted from Staphylococcus aureus plasmid pI258 (67 and 73% amino acid identities, respectively); however, only 40% of the amino acid residues of RC607 MerA were identical to those of the mercuric reductase from gram-negative bacteria. A 69-kilodalton polypeptide was isolated and identified as the merA gene product by examination of its amino-terminal sequence.
通过使用包含汞还原酶（merA）基因的克隆作为探针，从广谱耐汞芽孢杆菌属菌株RC607的染色体DNA中分离出一个带有完整汞抗性（mer）操纵子的13.5千碱基HindIII片段。新克隆pYW33在大肠杆菌和枯草芽孢杆菌中均表现出广谱汞抗性，但只有在枯草芽孢杆菌中汞还原酶活性是可诱导的。对一个产生汞超敏性的1.8千碱基片段进行测序，发现了四个开放阅读框（ORF）。ORF1可能编码一种调节蛋白（MerR）。ORF2和ORF4与细胞转运功能及超敏表型相关。对包含merA和merB基因的DNA片段进行了测序。预测的芽孢杆菌属菌株RC607的MerA（汞还原酶）和MerB（有机汞裂解酶）与从金黄色葡萄球菌质粒pI258预测的那些蛋白相似（分别有67%和73%的氨基酸同一性）；然而，RC607 MerA只有40%的氨基酸残基与革兰氏阴性菌的汞还原酶相同。通过检测其氨基末端序列，分离出一种69千道尔顿的多肽，并将其鉴定为merA基因产物。
