A RELA SPOT HOMOLOGOUS GENE FROM STREPTOMYCES-COELICOLOR A3(2) CONTROLS ANTIBIOTIC BIOSYNTHETIC GENES/

A 0.972-kilobase pair DNA fragment from Streptomyces lividans that ind uces the production of the blue-pigmented antibiotic actinorhodine in S, lividans when cloned on a multicopy plasmid has led to the isolatio n of a 4-kilobase pair DNA fragment from Streptomyces coelicolor conta ining homologous sequence, Computer-assisted analysis of the DNA seque nce revealed three putative open reading frames (ORFs), ORF1, ORF2, an d ORF3, ORF2 extends beyond the sequenced DNA fragment, and its deduce d product shares no similarities with any other known proteins in the data bases, ORF3 is also truncated, and its 41-amino acid C-terminal p roduct is identical 60 the S. coelicolor adenine phosphoribosyltransfe rase. The 847-amino acid ORF1 protein, with a predicted molecular mass of 94.2 kDa, strongly resembled the relA and spoT gene products from Escherichia coli and the homologs from Vibrio sp, strain S14, Haemophi lus influenzae, Streptococcus equisimilis H46A, and Mycoplasma genital ium, Unlike these proteins, the ORF1 amino acid sequence analysis reve aled the presence of a putative ATP/GTP-binding domain, A mutant was g enerated by deleting most of the ORF1 gene that showed an actinorhodin e-nonproducing phenotype, while undecylprodigiosin and the calcium-dep endent antibiotic were unaffected, The mutant strain grew at a much lo wer rate than the wild-type strain, and spore formation was delayed, W hen the gene was propagated on a low copy number vector, not only was actinorhodine production restored, but actinorhodine and undecylprodig iosin production was enhanced in both the mutant and wild-type strains and morphological differentiation returned to wild-type characteristi cs. (p)ppGpp synthetase activity was not detected in purified ribosome s from the ORF1-deleted mutant, while it was restored by complementati on of this strain.