IDENTIFICATION OF 2 NEW GENES IN THE PSEUDOMONAS-AERUGINOSA AMIDASE OPERON, ENCODING AN ATPASE (AMIB) AND A PUTATIVE INTEGRAL MEMBRANE-PROTEIN (AMIS)

The nucleotide sequence of the amidase operon of Pseudomonas aeruginos a has been completed and two new genes identified amiB and amiS. The c omplete gene order for the operon is thus amiEBCRS. The amiB gene enco des a 42-kDa protein containing an ATP binding motif that shares exten sive homology with the Clp family of proteins and also to an open read ing frame adjacent to the amidase gene from Rhodococcus erythropolis. Deletion of the amiB gene has no apparent effect on inducible amidase expression and it is thus unlikely to encode a regulatory protein, A m altose binding protein-AmiB fusion has been purified and shown to have an intrinsic ATPase activity (K-m = 174 +/- 15 mM; V-max = 2.4 +/- 0. 1 mM/min/mg), which is effectively inhibited by ammonium vanadate and ADP, The amiS gene encodes an 18-kDa protein with a high content of hy drophobic residues. Hydropathy analysis suggests the presence of six t ransmembrane helices in this protein, The AmiS sequence is homologous to an open reading frame identified adjacent to the amidase gene from Mycobacterium smegmatis and to the ureI gene from the urease operon of Helicobacter pylori. AmiS and its homologs appear to be a novel famil y of integral membrane proteins, Together AmiB and AmiS resemble two c omponents of an ABC transporter system.