Our laboratory studies nitric oxide (NO) biosynthesis in mammals and some of the related consequences of NO release. Discovered in 1987, this novel biochemical pathway is now considered to be a widespread means for host defense, regulation of cell function, and communication. Specific systems in which the pathway participates are signal transduction in the brain, stroke, control of blood pressure and heart rate, gastric motility, and immunologic destruction of tumor cells and microbes. Our main interests are in uncovering the enzyme reaction mechanism, understanding how enzyme structure relates to function, learning how other cellular proteins can control NOS activity, and the cell biology of NO as it relates to protein modifications.
The structure and biochemistry of nitric oxide synthases and related enzymes
Our goals are to enhance prevention, treatment and cures through research, and to develop innovative clinical programs for treating patients. The common research theme and the multi-disciplinary creative investigators in Pathobiology assure a continued high degree of successful collaborations, discoveries and innovation that allow us to realize these goals.
The NOS are controlled at multiple levels. We are studying how the active form of the enzyme is assembled within cells. At this point we know that intracellular heme availability determines how much of NOS is assembled into its active form, and that NO produced by the enzyme can prevent heme incorporation into the protein. Our understanding of assembly and its regulation may help develop a new means to control NO synthesis during inflammation. Another area of research involves activation of the neuronal and endothelial NOS by calcium. Two steps in the NOS electron transfer sequence are controlled by the calcium binding protein named calmodulin. Calmodulin enables electrons to pass to the iron atom, and also greatly speeds the introduction of electrons into the enzyme's flavin groups. We are now studying how calmodulin attachment changes the enzyme's structure and dynamics of its subdomain motions to allow these changes in electron transfer, using rapid spectroscopic techniques, single molecule spectroscopy, and mutants of calmodulin and NOS.
We are studying two aspects of NOS regarding cell biology. One project seeks to understand how NOS interactions with other cellular proteins such as caveolins or heat shock protein 90 modulate the assembly and activity of the NOS enzymes at a molecular level. A second project is focused on nitration of cellular proteins during NO synthesis- what components participate, how nitration can be selectively blocked, whether nitration causes change in protein function or gene expression, and whether enzymes exist that can remove or reduce the nitro group from proteins.
