Amide metabolism: a putative ABC transporter in Rhodococcus sp. R312

The DNA sequence has been determined upstream of the amiE structural gene in the amidase operon of Rhodococcus sp. R312 and a new ORF (amiS2) identified. The amiS2 gene encodes a potential 206 amino acid (aa) protein containing a high proportion of hydrophobic residues. The AmiS2 protein possesses high homology to the ORFP3, amiS and ureI gene products from the Mycobacterium smegmatis (Ms) acetamidase operon, Pseudomonas aeruginosa (Pa) amidase operon and Helicobacter pylori (Hp) urease operon, respectively. Hydropathic analysis and secondary structure prediction of AmiS2 suggested the presence of seven potential transmembrane (TM) alpha-helices. Sequence analysis of the amiB2 gene, located downstream of the Rhodococcus sp. R312 amiE gene, showed that it encoded a 351-aa protein containing a potential ATP-binding motif. AmiB2 showed significant homology with the ATP-binding subunit of the bacterial Clp protease and high homology with the amiB product located within the Pa amidase operon. AmiB2 and AmiS2 appear to be two components of a recently identified novel family of ABC transporters (Wilson et al., 1995) and might be responsible for the adsorption of amidase substrates or release of their hydrolysis products.