Transcriptional and functional analysis of the gene for factor C, an extracellular signal protein involved in cytodifferentiation of Streptomyces griseus.

Factor C is an extracellular signal protein involved in cellular differentiation in Streptomyces griseus. Nuclease S1 mapping experiments revealed that transcription of the gene takes place from a single promoter in a developmental-stage specific manner. The latter was also confirmed by in vivo promoter probing. The sequence of its promoter suggests that the gene is not transcribed by the major sigma factor. The cloned gene expressed from its own promoter in low- and high-copy-number vectors restored normal sporulation to a bald mutant of Streptomyces griseus. Computer analysis of the amino acid sequence revealed the presence of a transmembrane localization segment with the N-terminus positioned inside the cell. These data fit well into our working model that points at an important role for factor C in the morphogenesis of Streptomyces griseus.