Cloning and Functional Analysis of the pbr Lead Resistance Determinant of Ralstonia metallidurans CH34

Abstract

ABSTRACT The lead resistance operon, pbr , of Ralstonia metallidurans (formerly Alcaligenes eutrophus ) strain CH34 is unique, as it combines functions involved in uptake, efflux, and accumulation of Pb(II). The pbr lead resistance locus contains the following structural resistance genes: (i) pbrT , which encodes a Pb(II) uptake protein; (ii) pbrA , which encodes a P-type Pb(II) efflux ATPase; (iii) pbrB , which encodes a predicted integral membrane protein of unknown function; and (iv) pbrC , which encodes a predicted prolipoprotein signal peptidase. Downstream of pbrC , the pbrD gene, encoding a Pb(II)-binding protein, was identified in a region of DNA, which was essential for functional lead sequestration. Pb(II)-dependent inducible transcription of pbrABCD from the PpbrA promoter is regulated by PbrR, which belongs to the MerR family of metal ion-sensing regulatory proteins. This is the first report of a mechanism for specific lead resistance in any bacterial genus.