BenM and CatM are LysR-type transcriptional regulators (LTTR) that participate in the complex regulation of aromatic compound degradation by the soil bacterium Acinetobacter sp. Strain ADP1. While LTTRs comprise the largest family of bacterial transcriptional regulators, a clear understanding of their function has been hampered by past problems in characterizing atomic- level protein structures. These studies of BenM and CatM will use protein X-ray crystallography to examine structural changes underlying transcriptional activation. The conformational changes that occur in response to effector binding will be characterized. Furthermore, protein/DNA co- crystallization methods will address the structural basis for transmitting regulatory signals via alterations in protein-DNA interactions and evaluate the changes in protein conformations that enable two distinct effectors, benzoate and muconate, to have a synergistic effect on transcriptional activation by BenM. This type of dual-inducer synergy is a novel form of transcriptional regulation that may represent an important, and widespread, feature of transcriptional control. CatM, which has overlapping regulatory functions with BenM, responds only to muconate as an effector and thus provides a comparative model for identifying key structural features required for transcriptional synergism. BenM and CatM serve as a paradigm for complex transcriptional regulation and LTTR-controlled gene expression. Variant proteins and mutated promoter region DNA will also be characterized structurally. Previously proposed regulatory models will be tested by these structural studies. These studies of regulated aromatic compound degradation, in addition to expanding our understanding of bacterial transcriptional regulation, should increase the success of bioremediation of man-made pollutants and create new biotechnological applications.
