Transcriptional synergism in Acinetobacter

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These studies focus on aromatic compound degradation by the soil bacterium Acinetobacter sp. ADP1. Microbial catabolic pathways are good systems for studying biochemistry, genetics, and physiology. Moreover, their complex regulatory schemes can be exploited for biotechnology. In this project, mutational approaches will address the molecular basis of a novel synergism in transcriptional control. BenM is a LysR-type transcriptional regulator of benzoate catabolism that responds synergistically to two metabolites. The ability of one protein to integrate multiple cellular signals can effect rapid and large changes in gene expression. Understanding the response of BenM to effectors is important because it is a key representative of one of the largest groups of homologous regulators in bacteria. A successful collaboration with an X-ray crystallographer, Dr. Cory Momany, yielded well-characterized atomic level structures of the effector-binding domains of BenM and another paralog, CatM. Continued physiological investigations will test new regulatory models. Comparative studies between BenM and CatM provide unique opportunities to determine sequences that govern effector-regulated transcription. Although both regulators are similar in sequence and respond to the metabolite cis,cis-muconate, only BenM responds additionally to benzoate. The overlap in regulation between BenM and CatM will be used to dissect the functional significance of sequences in the proteins and in their target DNA promoters. These studies will elucidate complex regulatory circuits. Students will be trained in an important multidisciplinary area bridging microbial physiology and structural biology. Understanding LysR-type regulators has broad relevance for bioremediation and biotechnology, including the development of biosensors to detect harmful compounds.