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Transcript
Special Guest Speaker Dr. Christopher Colbert Chemistry and Biochemistry North Dakota State University Understanding Structure and Mechanism of Metalloproteins to Identify Novel Bio-Based Solutions Metalloproteins comprise approximately one-third of all proteins, and are critical for many of the biochemical processes responsible for life. Our longterm goal is to elucidate how cells import, incorporate, and utilize metals within proteins by using a combination of structural, biophysical, biochemical and molecular biology approaches. I will present two distinct projects in which we investigate how iron is used for biochemical processes involved in regulation of enzyme catalysis and gene expression to address challenges faced by modern human societies. Project 1: Rieske oxygenases are a diverse class of non-heme, mononuclear iron-containing enzymes capable of the stereo- and regio-selective insertion of molecular oxygen into aromatic substrates. These enzymes are important in the bioremediation of polyaromatic hydrocarbons and polychlorinated biphenyls (PCBs). However, only a few, such as biphenyl 2,3-dioxygenase from Pandoraea pnomenusa B-356 (BPDO), can potently degrade a large variety of PCB congeners. We have elucidated the structural basis for the broad PCB oxidation properties of BPDO, based on information from our structural studies combined with activity assays of selected mutants. These properties are probably rooted in the enzyme’s evolutionary interaction with secondary plant metabolites such as flavonoids. Our recent unpublished results suggest that the potent aromatic oxidizing properties of BPDO can be directed toward plant byproducts to make hydroxylated compounds with potentially two or three chiral centers, which may be exploited in natural product synthesis. Project 2: Cell-Surface Signaling (CSS) pathways in Gram-negative bacteria allow the cell to respond to extracellular stimuli. CSS pathways often involve three distinct proteins, 1) an outer membrane extracellular receptor, responsible for sensing the stimuli, 2) an inner membrane sigma factor regulator that transduces the signal from the periplasm to the cytoplasm, and a cytosolic sigma factor, which performs transcriptional regulation of stimulus response genes. A CSS pathway facilitates strict control of intracellular iron levels. Binding of an extracellular iron-laden siderophore to an outer membrane TonB-dependent transporter (TBDT) triggers CSS by inducing proteolytic degradation of the inner membrane sigma regulator. This releases the transcription factor to up-regulate transcription of the TBDT. We are investigating the Pseudomonas putida WCS358 pseudobactin BN7/8 system to understand this conserved process. Our studies reveal unique structural features with novel mechanistic implications for CSS. This information will guide future efforts to improve delivery of antibiotics to Gram-negative bacteria. February 20, 2017 3:00 PM ENV 125