Organization of genes responsible for the stereospecific conversion of hydantoins to alpha-amino acids in Arthrobacter aurescens DSM 3747

Arthrobacter aurescens DSM 3747 hydrolyzes stereospecifically 5 ' -monosubs tituted hydantoins to alpha -amino acids. The genes involved in hydantoin u tilization (hyu) were isolated on an 8.7-kb DNA fragment, and by DNA sequen ce analysis eight ORFs were identified. The hyu gene cluster includes four genes: hyuP encoding a putative transport protein, the hydantoin racemase g ene hyuA, the hydantoinase gene hyuH, and the carbamoylase gene hyuC. The f our genes are transcribed in the same direction. Upstream of hyuP and in op posite orientation to the hyu genes, three ORI's were found showing similar ities to cytochrome P450 monooxygenase (ORF1, incomplete), to membrane prot eins (ORF2), and to ferredoxin (ORF3). ORF8 was found downstream of hyuC an d again in opposite orientation to the hyu genes. The gene product of ORF8 displayed similarities to the LacI/GalR family of transcriptional regulator s. Reverse transcriptase PCR experiments and Northern blot analysis reveale d that the genes hyuPAHC are coexpressed in A. aurescens after induction wi th 3-N-CH3-IMH. The expression of the hyu operon was not regulated by the p utative regulator ORF8 as shown by gene disruption and mobility-shift exper iments.