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Marie-Alda Gilles-Gonzalez Assistant Professor Department of Biochemistry The Ohio State University Ohio State Biotechnology Center 244B Rightmire Hall 1060 Carmack Road Columbus, Ohio 43210-1002 Phone (614) 648-2079 email gilles-gonzalez.1@osu.edu	Back to Scientists

Research Interests

Mechanisms of Signal Transduction by Heme-Based Sensors

OUR RESEARCH aims to determine molecular mechanisms of signalling by O₂ and other heme ligands. In mammals, O₂ regulates red blood cell production, vascularization, and many other essential processes. Rhizobia detect their symbiotic association with leguminous plants and trigger the fixation of atmospheric nitrogen (N₂) into useful salts based on a drop in the available O₂. We have discovered and are continuing to characterize the first biological sensors of O₂, the FixL proteins. In Rhizobia, FixL, along with a transcription factor FixJ, form a classical two-component signal transduction system that regulates the expression of nitrogen fixation (nif, fix) genes. FixL is a kinase whose activity is reversibly inhibited by binding of O₂ to a heme-binding domain having a PAS fold. At low partial pressures of O₂, as occur within symbiotic root nodules, deoxy-FixL transfers a phosphoryl group from ATP to FixJ, enabling FixJ to activate the transcription of nif and fix genes. We have coined the term "heme-based sensors" to describe heme proteins that have evolved to sense, rather than carry or activate, heme ligands. Other heme ligands that can regulate FixL include nitric oxide (NO) and carbon monoxide (CO). NO is increasingly recognized as an important signal molecule that regulates processes such as vasodilation and neurotransmission in mammals. Our laboratory combines genetic, biochemical, biophysical, and structural approaches to study regulation by O₂ and other heme ligands. Some important areas of interest are: examination of heme-based sensors from other organisms; characterization of FixL mutants and homologs; determination of the mechanism of catalysis; examination of the three-dimensional structures of FixLs and FixJs. The methods used by our laboratory include the gamut of nucleic acid manipulations as well as protein purification and crystallization, assays of kinase and phosphatase activities, and measurements of the kinetics of reactions spaning milliseconds to hours. We work closely with collaborators to perform X-ray crystallography, as well as EPR, resonance Raman, and multi-dimensional NMR spectroscopy. Our research is supported in part by NSF grant MCB-9724048.

Selected References

• Delgado-Nixon, V. M., Gonzalez, G., and Gilles-Gonzalez, M. A. 2000 Dos, a heme-binding PAS protein from Escherichia coli is a direct oxygen sensor. Biochemistry In Press.
• Weimin Gong, Bing Hao, Sheref S. Mansy, Gonzalo Gonzalez, Marie A. Gilles-Gonzalez, and Michael K. Chan 1998 Structure of a biological oxygen sensor: a new mechanism for heme-driven signal transduction. Proceedings of the National Academy of Sciences, U.S.A. 95:15177-15182
• Sheref S. Mansy, John S. Olson, Gonzalo Gonzalez, and Marie A. Gilles-Gonzalez 1998 Imidazole is a sensitive probe of steric hindrance in the distal pockets of oxygen binding heme proteins. Biochemistry 37:12452-12457
• Gonzalo Gonzalez, Marie A. Gilles-Gonzalez, Elena V. Rybak-Akimova, Maria Buchalova, and Daryle H. Busch 1998 Mechanisms of autoxidation of the oxygen sensor FixL and Aplysia myoglobin: implications for oxygen-binding heme proteins. Biochemistry 37:10188-10194
• Wade W. Winkler, Gonzalo Gonzalez, Jonathan B. Wittenberg, Russ Hille, Naveen Dakappagari, Anand Jacob, Leyla A. Gonzalez, and Marie A. Gilles-Gonzalez 1996 Nonsteric factors dominate binding of nitric oxide, azide, imidazole, cyanide, and fluoride to the Rhizobial heme-based oxygen sensor FixL. Chemistry & Biology 3:841-850
• Craig Bertolucci, Li-June Ming, Gonzalo Gonzalez, and Marie A. Gilles-Gonzalez 1996 Assignment of the hyperfine-shifted 1H NMR signals of the heme in the oxygen sensor FixL from Rhizobium meliloti. Chemistry & Biology 3:561-566
• Marie A. Gilles-Gonzalez, Gonzalo Gonzalez, and Max F. Perutz 1995 Kinase activity of oxygen sensor FixL depends of the spin state of its heme iron. Biochemistry 34:232-236
• Marie A. Gilles-Gonzalez, Gonzalo Gonzalez, Max F. Perutz, Laurent Kiger, Michael Marden, and Claude Poyart 1994 Heme-based sensors, exemplified by the kinase FixL, are a new class of heme protein with distinctive ligand binding and autoxidation. Biochemistry 33:8067-8073
• Marie A. Gilles-Gonzalez and Gonzalo Gonzalez 1993 Regulation of the kinase activity of heme protein FixL from the two-component system FixL/FixJ of Rhizobium meliloti. J. Biol. Chem. 268:16293-7
• Marie A. Gilles-Gonzalez, Gary S Ditta, and Donald R. Helinski 1991 A haemoprotein with kinase activity encoded by the oxygen sensor of Rhizobium meliloti. Nature 350:170-172

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