Mrub_2120, Mrub_2121, Mrub_2122, Mrub_2123 and Mrub_2124 are orthologs of E. coli genes b3458, b3457, b3456, b3455 and b3454, respectively, and make up an operon that codes for the branched-chain amino acid ABC transporter in Meiothermus ruber DSM 1279