Selection and characterization of mercury-independent activation mutants of the Tn501 transcriptional regulator, MerR

作者：Parkhill J; Lawley B; Hobman JL; Brown NL^*

来源：Microbiology-SGM, 1998, 144: 2855-2864.

• repressor
• activator
• MerR family
• transposon
• mercury resistance

MerR is the transcriptional regulator of the mercury-resistance (mer) operon of transposon Tn501, acting at the mer promoter as both an activator in the presence of mercuric salts and a repressor in their absence. This paper reports a method for selection of constitutive activator mutants, which activate transcription in the absence of Hg-II, and the characterization of these MerR(AC) proteins. At least two mutations in the MerR protein were found necessary for strong mercury-independent activation, and these mutations lie in the C-terminal two-thirds of the MerR protein near the Hg-II-binding cysteines. A triple mutation was shown to increase activation over the corresponding double mutations. All mutant proteins caused further activation in the presence of Hg-II. The data support a mechanism in which a conformational change of one or both MerR subunits in the homodimer drives a distortion of DNA bound to a helix-turn-helix structure in the N-terminal region. A mutation in this putative helix-turn-helix region severely reduced both the repressor and activator functions of MerR.

• 出版日期1998-10