Identification of CfxR, an Activator Gene of Autotrophic CO2 Fixation in Alcaligenes Eutrophus

A regulatory gene, cfxR, involved in the carbon dioxide assimilation of Alcaligenes eutrophus H16 has been characterized through the analysis of mutants. The function of cfxR is required for the expression of two cfx operons that comprise structural genes encoding Calvin cycle enzymes. CfxR (34.8 kDa) corresponds with an open reading frame of 954 bp, with a translational initiation codon 167 bp upstream of the chromosomal cfx operon. The cfx operon and cfxR are transcribed divergently. The N-terminal sequence of CfxR is very similar to those of bacterial regulatory proteins belonging to the LysR family. Heterologous expression of cfxR in Escherichia coli was achieved using the pT7-7 system. Mobility shift experiments demonstrated that CfxR is a DNA-binding protein with a target site upstream of both the chromosomal and the plasmid-encoded cfx operons.