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John H. Richards
Professor of Organic Chemistry and Biochemistry

The research performed by Professor Richards' group is aimed at gaining a molecular understanding of the mechanisms of protein function in such areas as biological catalysis, the transport of electrons, and the exquisitely specific interactions between proteins and nucleic acids. In most of these studies the group uses altered proteins obtained by mutagenesis of the DNA coding for a protein, together with recombinant and cloning techniques. Chemically synthesized polypeptides and their derivatives also contribute importantly in this work.

Mutagenesis. Methods are being developed to allow alterations to be made at specific sites in the structural genes for proteins of interest. After cloning in an appropriate host, these genes direct the synthesis of the mutant proteins that are then studied to establish the molecular relationship between protein structure and function.

Catalysis. The group is examining a number of different enzymes to determine what structural features account for their ability to catalyze reactions by factors of 108 and more. Particular emphasis is placed on proteolytic enzymes, on enzymes responsible for antibiotic resistance in infectious microorganisms, and on DNA polymerases.

Electron Transport. During photosynthesis in green plants, electrons are transported between photosystems I and II by a blue copper protein, plastocyanin. (The single copper atom of the protein cycles between CuI and CuII in this process.) Analogous blue copper proteins, the azurins, carry out similar electron transport roles in bacteria. In understanding the biological roles of these proteins, the group probes questions such as: How do the four ligands to the copper influence its spectroscopic and redox properties, and what are the pathways of electron transfer from the copper atom to the surface of the protein, and then to other components of the electron transfer chain? Structural variants are also being created to allow attachment of ruthenium at specific locations on the surface of the protein for studies, in collaboration with Professor Gray's group, of the fundamental aspect of electron transfer between two metal centers (copper and ruthenium) that are separated from each other by precisely ascertainable (and variable) distances, and where the constitution of the intervening medium (the plastocyanin protein) can be exactly established. The group is also studying the copper A site, which plays a central role in the transfer of electrons to dioxygen during aerobic metabolism.