Hexacoordinate hemoglobins have been discovered that have yet to have a functional role confidently assigned to them. The eubacteria synechocystis sp. PCC 6803 has been found to have a truncated hemoglobin which is hexacoordinated. The structures of the hexacoordinated and cyanide bound forms of synechocystis hemoglobin have been solved, and a large shift in the E-helix has been seen upon ligand binding. Also, the loop connecting the E and F helix contains residues Tyr61 and Asp62 that are involved in hydrogen bonding networks in the cyanide-bound and hexacoordinate states respectively. A mutation was made to the Y61 residue to make it leucine, and this mutant protein was studied to investigate its role in regulating intramolecular histidine coordination to the heme iron. CO binding studies of flash photolysis and rapid mixing were performed to extract values for the CO binding rate and the rate of hexacoordination. The Y61L mutant protein has a rate of hexacoordination that is nearly 2.5 times greater than that of wild type synechocystis hemoglobin. Also, NMR spectra were taken on the wild type protein and it was revealed that a secondary conformation of the protein than that reported is present. Upon further inspection, it was suspected that the secondary conformation was most likely due to a covalent linkage to the heme from the H117 residue.
|Advisor:||Hargrove, Mark, Shogren-Knaak, Michael, Stauffer, Hans|
|School:||Iowa State University|
|Department:||Biochemistry, Biophysics, and Molecular Biology|
|School Location:||United States -- Iowa|
|Source:||MAI 46/01M, Masters Abstracts International|
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