STRUCTURAL INVESTIGATION OF NOVEL MUTANT HEMOGLOBINS

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Our laboratory has developed an E. Coli expression system for production of recombinant novel mutant hemoglobins induced by site-specific mutagenesis. One objective of this system is to design mutants that will allow us to assign resonance peaks in NMR spectra of human hemoglobin. We have thus designed and produced surface a-His to Gin mutant hemoglobins that have enabled us to assign some aromatic resonances. Some mutant hemoglobins have shown decrease in oxygen cooperativity, suggesting significant structural perturbation at the intersubunit region of hemoglobin tetramer. This is interesting, since the amino acid substitution is on the surface of the hemoglobin, $sim$30 $AA$ away from the intersubunit region, too far for anyone to suspect such prominent influence at the interface of the hemoglobin tetramer. We would like to investigate how a single amino acid substitution at the surface perturbs the interior sites of hemoglobin. We propose to use molecular dynamics to simulate the structural changes. We plan to use the stochastic boundary molecular dynamics method(SBMD) for simulation to reduce the processing time. We may have to resolve to including the entire protein in the calculation, however, since it is difficult to design a boundary that will include both the mutation site at the surface and the atoms at the intersubunit surface.