Binding characteristics of CebR, the regulator of the ceb operon required for cellobiose/cellotriose uptake in Streptomyces reticuli

The Streptomyces reticuli Avicelase (cellulase, Cell) hydrolyzes crystallin e cellulose to cellooligomers, cellobiose and cellotriose which are taken u p by mycelia via an ABC transport system (Ceb) induced during growth with c ellobiose or cellulose. The cebR gene located upstream of the cebEFG operon was cloned in Escherichia coli in frame with six histidine-encoding codons . The resulting purified fusion protein was shown to bind to a motif of 23 bp, including a perfect 18-bp palindrome situated upstream of the cebEFG. C ytoplasmic extracts of induced, but not of uninduced S. reticuli protected the same DNA motif. Release of the CebR regulator from its operator occurs upon addition of cellopentaose which can be assumed to act as inducer withi n the mycelia. (C) 2000 Federation of European Microbiological Societies. P ublished by Elsevier Science B.V. All rights reserved.