Do the hemeproteins behave as a dissipative structure?

Abstract

Continuing the search for a broader interpretation of hemeprotein behavior, we give preliminary results showing that there are electric and dynamic couplings between the heme group and amino acid residues within the protein matrix. EPR and X-ray absorption spectroscopy studies on azidometmyoglobin show that both magnetic and geometric properties of Fe-N, evolve in the same nonlinear way as pH is increased and are tightly correlated to the strains on the helical segments of the protein. Flash photolysis of carbon monoxide hemoglobin, in the presence of ethanol or formamide, allows the study of cosolvent effects on geminate and nongeminate recombinations of the CO ligand trapped within the protein matrix. Data clearly show that cosolvents alter the statistic fluctuations of the protein, as well as the ligand partition between different protein matrix domains. From these studies, it is concluded that alterations occurring at particular sites give way to global protein perturbations. Then, each perturbated protein domain-binding site included-evolves with its own sensitivity to a new metastable state of the protein. The amplification of the initial perturbation which-instead of regressing-progressively propagates through the whole macromolecule is typical of a dissipative structure in the Prigogine sense. Biological properties of hemeproteins largely involve the surrounding solvent, via permanent or temporary exchanges of water molecules, protons, and small ligands. These fluxes along with their entropic corollary are not quite compatible with a conservative system. These works present the current trends developed in our laboratory in association with the European network "The Dynamics of Protein Structure." In this framework, our laboratory collaborates with Dr. W. Doster and T. Kleinert (Munich, Germany) for the CO recombination studies in hemoglobin and with Dr.