M. Elliot et al., THE BLDD GENE OF STREPTOMYCES-COELICOLOR A3(2) - A REGULATORY GENE INVOLVED IN MORPHOGENESIS AND ANTIBIOTIC PRODUCTION, Journal of bacteriology, 180(6), 1998, pp. 1549-1555
The bid mutants of Streptomyces coelicolor A3(2) are blocked at the ea
rliest stage of sporulation, the formation of aerial hyphae, and are p
leiotropically defective in antibiotic production. Using a phage libra
ry of wild-type S. coelicolor DNA, se isolated a recombinant phage whi
ch restored both sporulation and antibiotic production to strains carr
ying the single known bldD mutation. Nucleotide sequence analysis of a
1.3-kb complementing subclone identified an open reading frame, desig
nated bldD, encoding a translation product of 167 amino acid residues.
Nucleotide sequence analysis of the bldD-containing fragment amplifie
d from the chromosome of a bldD mutant strain revealed a point mutatio
n changing a tyrosine residue at amino acid position 62 to a cysteine.
Although a comparison of the BldD sequence to known proteins in the d
atabases failed to show any strong similarities, analysis of the BldD
sequence for secondary structural elements did reveal a putative helix
-turn-helix, DNA recognition element near the C terminus of the protei
n. A comparison of bldD transcript levels in the bldD(+) and bldD muta
nt strains using both Northern blot analysis and SI nuclease protectio
n studies showed vast overexpression of bldD transcripts in the mutant
, suggesting that BldD negatively regulates its own synthesis. High-re
solution S1 nuclease mapping identified the transcription start point
as a G residue 63 nucleotides upstream from the bldD start codon and 7
nucleotides downstream from -10 and -35 sequences resembling E. coli-
like streptomycete promoters.