Hasona A, Self W T, Ray R M, Shanmugam K T
Department of Microbiology and Cell Science, University of Florida, Gainesville 32611, USA.
FEMS Microbiol Lett. 1998 Dec 1;169(1):111-6. doi: 10.1111/j.1574-6968.1998.tb13306.x.
In Escherichia coli, ModE-molybdate, a repressor of modABCD operon (molybdate transport), was previously shown to be an additional transcriptional activator of hyc operon (formate hydrogenlyase) and narGHJI operon (respiratory nitrate reductase). However, in a modE mutant, both operons were expressed at about 50% of the wild-type level in a molybdate-dependent manner. This ModE-independent, molybdate-dependent, expression of hyc, narG and narK operons required MoeA protein. An E. coli modE, moeA double mutant failed to produce formate hydrogenlyase or respiratory nitrate reductase activity irrespective of the growth medium. Tungstate substituted for molybdate in the activation of transcription of hyc and nar operons by ModE could not replace molybdate for MoeA-dependent expression. It is proposed that the MoeA-catalyzed product, an activated form of molybdate, interacts with a transcriptional activator/regulator other than ModE and regulates hyc and nar operons.
在大肠杆菌中，ModE-钼酸盐作为modABCD操纵子（钼酸盐转运）的阻遏物，先前已被证明是hyc操纵子（甲酸氢化酶）和narGHJI操纵子（呼吸型硝酸还原酶）的另一种转录激活剂。然而，在modE突变体中，这两个操纵子在钼酸盐依赖的方式下以野生型水平的约50%表达。hyc、narG和narK操纵子这种不依赖ModE、依赖钼酸盐的表达需要MoeA蛋白。无论生长培养基如何，大肠杆菌modE、moeA双突变体都无法产生甲酸氢化酶或呼吸型硝酸还原酶活性。在ModE对hyc和nar操纵子转录激活过程中，钨酸盐可替代钼酸盐，但在MoeA依赖的表达中，钨酸盐无法替代钼酸盐。有人提出，MoeA催化的产物，即一种活化形式的钼酸盐，与ModE以外的转录激活剂/调节因子相互作用，并调节hyc和nar操纵子。
