Cobalt-dependent transcriptional switching by a dual-effector MerR-like protein regulates a cobalt-exporting variant CPx-type ATPase
Cobalt-dependent transcriptional switching by a dual-effector MerR-like protein regulates a cobalt-exporting variant CPx-type ATPase
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DOI：
10.1074/jbc.274.36.25827
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发表时间：
1999-09-03
影响因子：
4.8
通讯作者：
Robinson, NJ
中科院分区：
文献类型：
--
作者：
Rutherford, JC;Cavet, JS;Robinson, NJ
CoaR与coaT操纵子-启动子结合并赋予coaT操纵子-启动子的钴依赖性激活。羧基末端Cys-His-Cys基序中的CoaR突变体（Ser-Asn-Ser）结合coaT操纵子启动子，但不会响应钴而激活表达，这表明这些残基上的硫醇盐和/或咪唑配体位于变构钴结合位点中。在接近共有序列之间缺失1或2个核苷酸，但存在异常（20个碱基对）间隔，-10和-35元件增强了coaT操纵子-启动子的表达，但消除了钴-CoaR的激活。推断钴影响CoaR中的转变，该转变使coaT操纵子-启动子下旋以重新排列启动子元件。在不存在钴的情况下，CoaR抑制表达（类似于50%）。CoaR是祖先MerR（汞响应性转录激活因子）和前受体异构酶（维生素B-12生物合成酶）相关序列的融合体。在cbiE（编码B-12生物合成中前受体蛋白异构酶之前的酶）的部分突变体中，来自coaT操纵子-启动子的表达增强，揭示了该途径“抑制”coaT表达。破坏coaT降低钴耐受性和增加细胞质Co-57积累。coaT介导的钴耐受性恢复已被用作选择标记。
CoaR associates with and confers cobalt-dependent activation of the coaT operator-promoter. A CoaR mutant (Ser-Asn-Ser) in a carboxyl-terminal Cys-His-Cys motif bound the coaT operator-promoter but did not activate expression in response to cobalt, implicating thiolate and/or imidazole ligands at these residues in an allosteric cobalt binding site. Deletion of 1 or 2 nucleotides from between near consensus, but with aberrant (20 base pairs) spacing, -10 and -35 elements enhanced expression from the coaT operator-promoter but abolished activation by cobalt-CoaR, It is inferred that cobalt effects a transition in CoaR that underwinds the coaT operator-promoter to realign promoter elements, In the absence of cobalt, CoaR represses expression (similar to 50%). CoaR is a fusion of ancestral MerR (mercury-responsive transcriptional activator)- and precorrin isomerase (enzyme of vitamin B-12 biosynthesis)-related sequences. Expression from the coaT operator-promoter was enhanced in a partial mutant of cbiE (encoding an enzyme preceding precorrin isomerase in B-12 biosynthesis), revealing that this pathway "inhibits" coaT expression. Disruption of coaT reduced cobalt tolerance and increased cytoplasmic Co-57 accumulation. coaT-mediated restoration of cobalt tolerance has been used as a selectable marker.