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Hydrogen-tritium exchange titration of the histidine residues in bovine heart cytochrome c and analysis of their microenvironment.

S Kitmura·H Matsuo·K Narita
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Abstract

Microenvironments of the three histidine residues located at the positions 18, 26, and 33 from the amino terminus in bovine heart cytochrome c were analysed in solution by the hydrogen-tritium exchange titration method, which has been developed in this laboratory. Histidine-18, which is liganded to the heme iron, and histidine-26 did not incorporate tritium in native state, indicating that the two are located in solvent inaccessible hydrophobic regions. Histidine-33 was labeled with tritium to an appreciable extent and seemed to be partially buried in the molecule. The pKa value estimated for histidine-33 was 6.1 at 37 degrees by the tritium exchange titration, suggesting that the residue interacts very weakly with a neighboring cationic group. These results seem to be compatible with the tertiary structure of the protein deduced from the X-ray crystallographic analysis.

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Amino Acid SequenceAmino AcidsAnimalsCattleChemical PhenomenaChemistryCytochrome c GroupHistidineHydrogenHydrogen-Ion ConcentrationMyocardiumTritiumJournal Article

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S Kitmura, H Matsuo, K Narita. 1979. Hydrogen-tritium exchange titration of the histidine residues in bovine heart cytochrome c and analysis of their microenvironment.. https://doi.org/10.1111/j.1399-3011.1979.tb01958.x

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