MetJ regulators are transcriptional repressors of genes involved in methionine and S-adenosylmethionine biosynthesis and methionine uptake in Gammaproteobacteria. MetJ repressor recognizes its binding sites that are organized as tandem repeats of an 8 bp sequence (the met-box), which varies around a consensus sequence of dAGACGTCT. There are two to five such sequences tandemly repeated in natural operators. In the presence of effector, S-adenosylmethionine, DNA-affinity of the regulator highly increases . MetJ regulators are characterized by a ribbon-helix-helix (RHH) DNA binding motif (PF01340) .
Recently, the likely composition of the MetJ regulon in all species which have MetJ orthologs was determined by using bioinformatics techniques [22082356