Mercury is a known toxic metalloid that can inhibit many biochemical processes. The mer operon which encode mercuric resistance have been found in multicopy plasmids in both gram negative and gram positive bacteria. This operon contains several important genes include merA, merB, merTandmerRrespectively. Several researches based on molecular techniques showed obvious homology of this operon in plasmids among number of bacterial species. These results suggest that the mer operons have an evolutionary precursor from an ancient strain. Moreover, the experimental studies indicated that mer operons in bacterial plasmids maybe have different sensitivity to
mercury compounds. One of the probable factors for this phenomenon may be merR gene (the first cistron of mer operon) and its product, MerR protein, which is a trans-acting repressor that regulates expression of mer operon. The overall goal of our study was to carry out a set of comparative analyses of merR gene and MerR protein in
plasmid pBS228 from Pseudomonas aeruginosa and merR gene and protein from Escherichia coli MS 145 to understand which of them are more sensitive than another. Methods : PDB and NCBI databases and Chimera, Mega4, CLC main workbench softwares and CPHmodels 3.2 Server and Prosite servers were applied to perform this study. By using these softwares and servers, multiple analyses including determination of residue composition, secondary structure and motifs, 3D structure, conserved regions, etc. were applied. Results : Our results suggest that the sensitivity of mer operon in
plasmid pBS228 to
mercury compound is more than another one from E.coli MS 150. Conclution : This deduction may be due to the related MerR protein characteristics such as amino acids composition in alpha helix regions, secondary and tertiary structure, level of interaction with DNA, the N-terminal Hg2+ binding site etc. In addition, our phylogenetic analyses suggest that there is an interesting evolutionary relationship in prokaryotes based on merR gene.