title: Structural Basis of Selective Aromatic Pollutant Sensing by the Effector Binding Domain of MopR, an NtrC Family Transcriptional Regulator.
abstract: Phenol and its derivatives are common pollutants that are present in industrial discharge and are major xenobiotics that lead to water pollution. To monitor as well as improve water quality, attempts have been made in the past to engineer bacterial in vivo biosensors. However, due to the paucity of structural information, there is insufficiency in gauging the factors that lead to high sensitivity and selectivity, thereby impeding development. Here, we present the crystal structure of the sensor domain of MopR (MopR(AB)) from Acinetobacter calcoaceticus in complex with phenol and its derivatives to a maximum resolution of 2.5 Å. The structure reveals that the N-terminal residues 21-47 possess a unique fold, which are involved in stabilization of the biological dimer, and the central ligand binding domain belongs to the "nitric oxide signaling and golgi transport" fold, commonly present in eukaryotic proteins that bind long-chain fatty acids. In addition, MopR(AB) nests a zinc atom within a novel zinc binding motif, crucial for maintaining structural integrity. We propose that this motif is crucial for orchestrated motions associated with the formation of the effector binding pocket. Our studies reveal that residues W134 and H106 play an important role in ligand binding and are the key selectivity determinants. Furthermore, comparative analysis of MopR with XylR and DmpR sensor domains enabled the design of a MopR binding pocket that is competent in binding DmpR-specific ligands. Collectively, these findings pave way towards development of specific/broad based biosensors, which can act as useful tools for detection of this class of pollutants.
authors.affiliation: IITB-Monash Research Academy , Mumbai 400076, Maharashtra, India.
authors.forename: Shamayeeta
authors.initials: S
authors.lastname: Ray
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Menachem J
authors.initials: MJ
authors.lastname: Gunzburg
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University , Clayton, Victoria 3800, Australia.
authors.forename: Matthew
authors.initials: M
authors.lastname: Wilce
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University , Clayton, Victoria 3800, Australia.|Australian Synchrotron , Clayton, Victoria 3168, Australia.
authors.forename: Santosh
authors.initials: S
authors.lastname: Panjikar
authors.affiliation: Department of Chemistry, Indian Institute of Technology Bombay , Mumbai 400076, Maharashtra, India.|Wadhwani Research Center for Bioengineering, IIT Bombay , Mumbai 400076, India.
authors.forename: Ruchi
authors.initials: R
authors.lastname: Anand
mesh_terms: D000150:Acinetobacter / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015374:Biosensing Techniques; D018360:Crystallography, X-Ray; D019281:Dimerization; D004785:Environmental Pollutants / Q000032:analysis*; D015964:Gene Expression Regulation, Bacterial; D008024:Ligands; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004785:Environmental Pollutants; D008024:Ligands; C104241:MopR protein, Acinetobacter calcoaceticus; D015534:Trans-Activators