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Journal of Bacteriology, May 2008, p. 3336-3343, Vol. 190, No. 9
0021-9193/08/$08.00+0     doi:10.1128/JB.00033-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

RcoM: A New Single-Component Transcriptional Regulator of CO Metabolism in Bacteria

Department of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin 53706

Received 8 January 2008/ Accepted 19 February 2008

Genomic analysis suggested the existence of a CO-sensing bacterial transcriptional regulator that couples an N-terminal PAS fold domain to a C-terminal DNA-binding LytTR domain. UV/visible-light spectral analyses of heterologously expressed, purified full-length proteins indicated that they contained a hexacoordinated b-type heme moiety that avidly binds CO and NO. Studies of protein variants strongly suggested that the PAS domain residues His74 and Met104 serve as the heme Fe(II) axial ligands, with displacement of Met104 upon binding of the gaseous effectors. Two RcoM (regulator of CO metabolism) homologs were shown to function in vivo as CO sensors capable of regulating an aerobic CO oxidation (cox) regulon. The genetic linkage of rcoM with both aerobic (cox) and anaerobic (coo) CO oxidation systems suggests that in different organisms RcoM proteins may control either regulon type.

Published ahead of print on 7 March 2008.