MOLECULAR ANALYSIS OF AN OPERON IN BACILLUS-SUBTILIS ENCODING A NOVELABC TRANSPORTER WITH A ROLE IN EXOPROTEIN PRODUCTION - SPORULATION AND COMPETENCE

The levels of exoamylase and other exoenzymes of Bacillus subtilis are pleiotropically decreased by the ecs-26 (prs-26) and ecs-13 (prs-13) mutations. These mutations also cause a competence- and sporulation-de ficient phenotype. In the present work, the ecs locus, which has been defined by the ecs-26 and ecs-13 mutations, was cloned and sequenced. Sequence analysis revealed a putative operon of three ORFs (ecsA, ecsB and ecsC). ecsA can encode a putative polypeptide of 248 amino acid r esidues containing an ATP-binding site. The polypeptide shows about 30 % sequence similarity with the ATP-binding components of numerous memb rane transporters of the ABC-type (ATP-binding cassette transporters o r traffic ATPases), The ecs-26 mutation was found to result from a tra nsition of one base pair changing the glycine(164) of EcsA to a glutam ic acid residue in the vicinity of the putative ATP-binding pocket, ec sB was predicted to encode a hydrophobic protein with six membrane-spa nning helices in a pattern found in other hydrophobic components of AB C transporters. The properties deduced for the ecsA and ecsB gene prod ucts are consistent with the interpretation that ecs encodes a novel A BC-type membrane transporter of B. subtilis. The third ORF, ecsC, can encode a putative polypeptide of 237 amino acid residues. The polypept ide does not resemble components of ABC transporters.