| The DNA-binding transcriptional regulator, BldD, may function as both a repressor and an activator of developmental and antibiotic synthesis genes in Streptomyces coelicolor. Specific modification of the BldD protein itself, or the interaction of BldD with a binding partner, are two of the possibilities for how BldD activity might be modulated. A number of biochemical techniques were employed to address these two possibilities. Although these methods did not lead to characterization of a modified BldD protein or a BldD-binding partner, two-dimensional separation of S. coelicolor cell-free extract proteins identified at least three putative modified BldD isoforms and chemical crosslinking studies identified a possible BldD protein complex. Further support for the activator function of BldD was obtained by chromatin immunoprecipitation analyses, which indicated that BldD could bind in vivo to the sigQ promoter, a putative activated target of BldD. Semi-quantitative RT-PCR results suggested that sigQ expression is activated by BldD. |
