STUDIES OF THE DYNAMICS OF HEME PROTEIN ACTIVE SITES

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The work described in this proposal is an extension of our continuing effort to describe and compare the active site dynamics of two unique heme proteins. One of these is cytochrome c peroxidase, a ferriheme enzyme isolated from baker's yeast in the laboratory of Dr. James Erman. The other protein is actually a group of proteins which have been individually isolated and purified in my own laboratory and which comprise the so called "Monomer Hemoglobin" fraction of Glycera Dibranchiata. Cytochrome c peroxidase (CcP) has been studied by less precise spectroscopic methods, but our initial work has shown that proton nuclear magnetic resonance spectroscopy can be used effectively to identify the role played by specific groups, both on the protein and on the heme group, which influence the enzyme's reactivity (vide infra, see also the reprints and preprints). We plan to continue our dynamics studies with nmr employing saturation transfer and Redfield pulse sequence experiments. These will result in further assignments of hyperfine shifted protons, analysis of heme binding dynamics, elucidation of the lability of hyperfine shifted protons and quantitation of the extent of communications between extrinsic molecules and the individual atoms which are components of the active site. Our work on the second group of proteins is on the verge of rapid expansion during the present year due to our efforts during the recent past at purifying the Glycera monomer fraction. Of prime importance in this effort is the fact that one of these components has been determined to lack the distal histidine. Studies of these proteins will include ligation dynamics, equilibrium ligation studies and these will be related to the spectroscopic characterization of the heme pocket in conjunction with sequence and structural studies carried out elsewhere. Conclusions drawn from these studies will have extensive impact upon theories of the particular role which distal residues play in both cooperative and non-cooperative ligand binding processes. These will be true structure-function correlations which may define specific factors which govern the primary process (ligand binding) of non-covalent heme proteins. The results of this research will impact the design of synthetic heme enzymes and tailored heme proteins.