3F2H

Crystal structure of the mercury-bound form of MerB mutant C160S, the Organomercurial Lyase involved in a bacterial mercury resistance system

Summary for 3F2H

• Entry DOI: 10.2210/pdb3f2h/pdb
• Related: 1s6l 3F0O 3F0P 3F2F 3F2G
• Descriptor: Alkylmercury lyase, MERCURY (II) ION (3 entities in total)
• Functional Keywords: merb, organomercurial lyase, alkylmercury lyase, mercury resistance, mercuric resistance, plasmid, lyase
• Biological source: Escherichia coli
• Total number of polymer chains: 2
• Total formula weight: 48627.89

Authors

Lafrance-Vanasse, J.,Lefebvre, M.,Di Lello, P.,Sygusch, J.,Omichinski, J.G. (deposition date: 2008-10-29, release date: 2008-11-11, Last modification date: 2023-09-06)

Primary citation

Lafrance-Vanasse, J.,Lefebvre, M.,Di Lello, P.,Sygusch, J.,Omichinski, J.G.
Crystal Structures of the Organomercurial Lyase MerB in Its Free and Mercury-bound Forms: INSIGHTS INTO THE MECHANISM OF METHYLMERCURY DEGRADATION
J.Biol.Chem., 284:938-944, 2009

PubMed Abstract: Bacteria resistant to methylmercury utilize two enzymes (MerA and MerB) to degrade methylmercury to the less toxic elemental mercury. The crucial step is the cleavage of the carbon-mercury bond of methylmercury by the organomercurial lyase (MerB). In this study, we determined high resolution crystal structures of MerB in both the free (1.76-A resolution) and mercury-bound (1.64-A resolution) states. The crystal structure of free MerB is very similar to the NMR structure, but important differences are observed when comparing the two structures. In the crystal structure, an amino-terminal alpha-helix that is not present in the NMR structure makes contact with the core region adjacent to the catalytic site. This interaction between the amino-terminal helix and the core serves to bury the active site of MerB. The crystal structures also provide detailed insights into the mechanism of carbon-mercury bond cleavage by MerB. The structures demonstrate that two conserved cysteines (Cys-96 and Cys-159) play a role in substrate binding, carbon-mercury bond cleavage, and controlled product (ionic mercury) release. In addition, the structures establish that an aspartic acid (Asp-99) in the active site plays a crucial role in the proton transfer step required for the cleavage of the carbon-mercury bond. These findings are an important step in understanding the mechanism of carbon-mercury bond cleavage by MerB.

PubMed: 19004822
DOI: 10.1074/jbc.M807143200

Experimental method

X-RAY DIFFRACTION (2 Å)