Molecular analysis of sporulation in Streptomyces griseus.

Previous evidence suggested that orf1590 from Streptomyces griseus has the potential to encode two polypeptide products from temporally regulated nested open frames (orfs) and that the longer polypeptide may be a DNA-binding protein. We have developed a hypothetical model of the role of orf1590 in sporulation of S. griseus and have begun to test this model by determining the nucleotide sequence of the orf1590 counterpart from Streptomyces coelicolor. The conservation of the helix-turn-helix domain and the two potential translation start codons is consistent with our model. Continued analysis of bald mutants of S. griseus has indicated that several prematurely synthesize sporulation septa and spore walls. One of these nonsporulating strains appears to be a bldA mutant of S. griseus. Complementation analysis suggests that at least three genetic loci are involved in the correct timing of deposition of sporulation septa and wall thickening.