Faculty Research Interest

Protein Folding; Molecular Mechanisms of Cytochrome Oxidase and Nitric Oxide Synthase

Faculty Record

In our laboratory the mechanisms and properties of two enzymes, cytochrome c oxidase and nitric oxide synthase, are being investigated as well as the molecular basis of protein folding.

Cytochrome c oxidase is the terminal enzyme in the electron transfer chain. Physiologically, it reduces oxygen to water and utilizes the excess energy to translocate protons across the mitochondrial membrane. The enzyme is responsible for over 90% of the oxygen consumption by living organisms in the biosphere; yet the mechanism of its basic function, the coupling between the redox processes and proton translocation is undetermined. Our objective is to obtain a quantitative description of the manner by which oxygen is reduced to water by exploiting laser spectroscopic methods and rapid mixing techniques developed in our laboratory. These studies will allow us to identify all of the intermediates in the catalytic reaction and thereby establish the molecular basis for one of the most important processes in bioenergetics.

Nitric oxide has been found to play many diverse physiological roles ranging from a neurotransmitter, a vasodilator and a cytotoxic agent. The enzyme that catalyzes the formation of NO from oxygen and arginine is nitric oxide synthase, a very complex enzyme containing several cofactors and a heme group which is part of the catalytic site. We have discovered that NO the enzymatic product, inhibits the enzyme and are now studying the mechanism of the inhibition process. In addition, we are studying a variety of inhibitors of the enzyme to sort between the many mechanisms of inhibition that are possible in nitric oxide synthase. These studies will serve as a foundation for the development of drugs that can be used to treat many different syndromes associated with the under- or over-production of NO.

How a protein folds into its three dimensional structure is one of the central questions in molecular biology and in the biotechnology industry. To advance the understanding of protein folding, it is necessary to determine the structures and the kinetics of the intermediates in the folding pathway. For this, we developed submillisecond mixers in which folding can be initiated in less than 100 microseconds, a time scale that is over an order of magnitude faster than previously possible. This already has allowed us to discover a new model that accounts for the folding of cytochrome c from 100 microseconds to the formation of the native state. Many new experiments with several different techniques will be done to test the generality of this model and its possible role in other proteins.