Abstract
As an approach to an analysis of the biosynthesis of the aminoglycoside antibiotic butirosin (But), we investigated the chromosomal regions flanking the But R gene ( aphA4/butA) of Bacillus circulans NRRL-B3312, and have identified, by nucleotide sequence analysis, a large open reading frame (ORF; ButB) upstream from the But R gene. Hybridization was detected between butB and chromosomal DNA from other Bacillaceae that produce But-like compounds (but not from non-producers). Interruption of this sequence by insertion of an erythromycin-resistance-encoding gene ( erm) at either of two distinct sites eliminated the production (biosynthesis or export) of But, thus indicating a role for butB in antibiotic production. Gene butB is transcribed in the same direction as but A and encodes a protein of 1616 amino acid (aa) residues with a 30-aa N-terminal signal peptide. Comparison of the sequence for the translation product (ButB) with the aa compositions and sequences of known bacterial surface proteins, such as S-layer proteins, suggests that this protein is cell-wall associated. It is proposed that ButB plays a role in the export of But from the producing organism.
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