The nucleotide sequence of a 12-kilobase region covering
afsA encoding a key enzyme for A- factor biosynthesis in
Streptomyces griseus was determined and open reading frames were deduced by means of G+C plot analysis. Although this region about 150-kb from one end of the linear chromosome is known to be readily deleted, open reading frames crowd the region in a total of eleven, including
afsA and
sgaA involved in healthy growth on medium of high osmolality. These also include a pair of a sensor histidine kinase and a regulator which comprises a typical prokaryotic two-component regulatory system, proteins similar to
O-methyltransferase, LysR-type regulator, 3-ketoacyl-acyl carrier protein reductase, and NADP-dependent alcohol dehydrogenase. In contrast to
afsA-like genes in other
Streptomyces strains, such as
barX locating closely to the gene for the virginiae butanolide receptor in
Streptomyces virginiae and
farX locating closely to the IM-2-receptor gene in a
Streptomyces sp., no open reading frames in this region in
S. griseus show homology with the A-factor receptor protein, which suggests that the gene organization of receptor genes for γ-butyrolactone autoregulators differs from strain to strain.
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