This research program is centered around the application of protein crystallography (a form of microscopy which uses X-rays in place of light rays) to directly produce high resolution images of protein structure. Much of our research effort has been aimed at achieving a more detailed understanding of the relationships between hemoglobin structure and function. In particular, we have determined the structures of a number of variant and chemically modified hemoglobins. By identifying the differences between the structures of these abnormal hemoglobins and normal human deoxyhemoglobin we have been able to 1) pinpoint structural features which are essential for full expression of hemoglobin function, 2) suggest a structural basis for the action of a number of drugs which have been shown to be effective in reducing the polymerizaion of sickle cell hemoglobin, and 3) uncover anion binding sites which may be important in the interaction of hemoglobin with CO2. In collaboration with Dr. David Metzler at Iowa State University we are also studying the crystal of aspartate aminotransferase purified from pig heart. Currently, we are analyzing a 2.7 A electron density map of the enzyme as well as studying complexes of the enzyme with substrates and inhibitors. Our studies should reveal structural details which will be useful in understanding the mechanism of action of this enzyme as well as of the large class of enzymes which used pyridoxal phosphate as a coenzyme. More recently, we have started studies aimed at crystallizing specific fragments of DNA and DNA-protein complexes. The work is still in its initial stages, but we hope that eventually it will add to our understanding of the structural aspects of DNA-protein interactions.
