4ua2 | pdb_00004ua2
Crystal structure of dual function transcriptional regulator MerR from Bacillus megaterium MB1
Structural highlights
FunctionQ799U3_PRIMG Mediates the mercuric-dependent induction of mercury resistance operon. In the absence of mercury MerR represses transcription by binding tightly to the mer operator region; when mercury is present the dimeric complex binds a single ion and becomes a potent transcriptional activator, while remaining bound to the mer site.[ARBA:ARBA00024874] Publication Abstract from PubMedThe mer operon confers bacterial resistance to inorganic mercury (Hg2+) and organomercurials by encoding proteins involved in sensing, transport and detoxification of these cytotoxic agents. Expression of the mer operon is under tight control by the dual-function transcriptional regulator MerR. The metal-free, apo MerR binds to the mer operator/promoter region as a repressor to block transcription initiation, but is converted into an activator upon Hg2+-binding. To understand how MerR interacts with Hg2+ and how Hg2+-binding modulates MerR function, we report here the crystal structures of apo and Hg2+-bound MerR from Bacillus megaterium, corresponding respectively to the repressor and activator conformation of MerR. To our knowledge, the apo-MerR structure represents the first visualization of a MerR family member in its intact and inducer-free form. And the Hg2+-MerR structure offers the first view of a triligated Hg2+-thiolate center in a metalloprotein, confirming that MerR binds Hg2+ via trigonal planar coordination geometry. Structural comparison revealed the conformational transition of MerR is coupled to the assembly/disassembly of a buried Hg2+ binding site, thereby providing a structural basis for the Hg2+-mediated functional switching of MerR. The pronounced Hg2+-induced repositioning of the MerR DNA-binding domains suggests a plausible mechanism for the transcriptional regulation of the mer operon. Structural basis of the mercury(II)-mediated conformational switching of the dual-function transcriptional regulator MerR.,Chang CC, Lin LY, Zou XW, Huang CC, Chan NL Nucleic Acids Res. 2015 Jul 6. pii: gkv681. PMID:26150423[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
| ||||||||||||||||||
