Abstract
Crown gall tumors incited by A. tumefaciens release compounds called opines, which serve as nutrient sources and as signal molecules for the colonizing bacteria. One such opine, octopine, induces expression of a cognate catabolism operon (occQ) via a LysK-type protein called OccR. Here we describe biochemical properties of complexes formed between OccR and operator DNA. This regulatory system was reconstituted in vitro using purified OccR protein and Escherichia coli RNA polymerase. OccR binds with high affinity to a single site overlapping the divergent occQ and occR promoters. Octopine increases the gel mobility of OccR-DNA complexes, relaxes an OccR-incited DNA bend, and shortens the DNase I footprint of OccR. This operator contains a 6 bp dyad symmetry in its left half and an unrelated 4 bp dyad symmetry in its right half. A 19 bp region including the right dyad is necessary and sufficient for high affinity OccR binding; while a larger region including both the left and right dyads is necessary for DNA bending and transcriptional repression.
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© 1993 Springer Science+Business Media Dordrecht
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Wang, L., Cho, K., Helmann, J.D., Winans, S.C. (1993). The Agrobacterium Tumefaciens Transcriptional Activator OccR Causes a Bend at a Target Promoter that is Partially Relaxed by a Plant Tumor Metabolite. In: Nester, E.W., Verma, D.P.S. (eds) Advances in Molecular Genetics of Plant-Microbe Interactions, Vol. 2. Current Plant Science and Biotechnology in Agriculture, vol 14. Springer, Dordrecht. https://doi.org/10.1007/978-94-017-0651-3_13
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DOI: https://doi.org/10.1007/978-94-017-0651-3_13
Publisher Name: Springer, Dordrecht
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