A PUTATIVE TRANSCRIPTION FACTOR-BINDING TO THE UPSTREAM REGION OF THEPUF OPERON IN RHODOBACTER-SPHAEROIDES

Gel shift assays of the upstream region of the puf operon in Rhodobact er sphaeroides were performed using cell-free extracts from cells grow n under various culture conditions. The results suggested that a prote in binding to the upstream region functioned as a repressor-like subst ance of the expression of the operon by oxygen tension or light. The d ensity of the shifted band of cell-free extracts from cells irradiated with blue light under semi-aerobic conditions was higher than that wi th red light. Phosphatase treatment of the cell-free extracts strongly increased the DNA-binding affinity of the protein.