Difference between revisions of "Part:BBa K1420001"

Revision as of 23:57, 12 October 2014

merA, mercuric reductase from Serratia marcescens

Overview

MerA, a cytoplasmic mercuric ion reductase, is the essential component of bacterial mercury resistance. MerA couples with the organomercurial lyase, MerB to reduce the toxicity of organic and inorganic mercury compounds. While MerA and MerB are the key mercury detoxification enzymes, they orchestrate with mercury transport proteins, MerT and MerP, to confer bacterial mercury resistance.

Figure 1 shows the interactions of MerA, mercury compounds, and other mer proteins. MerA and gene merA are highlighted in orange.merA is located downstream of mer genes that encodes mercury transport proteins. Organic mercury such as methylmercury commonly binds to thiol groups and forms strong but reversivle bonds that are partial covalent, partial ionic bonds.

Figure 1. Model of mercury resistance operon. The symbol • indicates a cysteine residue. RSH indicates cystosolic thiol redox buffers such as glutathione. (This figure is adapted from "Bacterial mercury resistance from atoms to ecosystems". Reference: T. Barkay et al. FEMS Microbiology Reviews 27 (2003) 355-384.)

Molecular Function

MerA catalyzes the reduction of mercuric ion to the relative inert, volatile monoatomic mercury in a NADPH dependent reaction.

Scheme 1. MerA Catalyzed Reaction

Structure and Mechanism

Characterization of merA

To test the effect of MerA to the level of mercury resistance, we generated a merA deletion mutant and characterized it by zone of inhibition test.

Zone of Inhibition Results

Figure 2. Zones of Inhibition Test For Mercury Resistance Activity. Three different plasmids were expressed in Escherichia coli strain K12 to compare level of mercury resistance. (A)Plates of ZOI test. Left, K12 conntaining pBBRBB::mer; center,K12 containing pBBRBB::gfp; right, K12 strain containing pBBRBB::merΔmerA, or the merA deletion mutant. (b) Graphical representation of the size of zones of inhibition diameter. The diameter of the Zone of Inhibition was measured in triplicate. Green corresponds to pBBRBB::gfp, blue to pBBRBB::mer, and red to pBBRBB::merΔmerA.

Sequence and Features