Studies On The Interaction Between Metal Ions And Bovine Hemoglobin

The function of a bio-molecule usually depends on its specific, non-covalent interaction with other molecules. For example: proteins interact with other proteins, peptides, small-molecules, metal ions, lipids, polysaccharides, nucleic acids and oligonucleotides. These interactions drive critically important cellular processes such as cell division, cell signaling, ion transportation, homeostasis, gene transcription, and translation, etc.The hemoglobin is a multisubunit protein; its physiological function is well correlated with its particular structure. It ensures oxygen transport to all organs and parts of the body, and posses a certain capacity to act as a buffer in the blood of living organisms.The binding of metal ions to protein is a very critical theme for biochemistry. There are a few research publications concerning the interaction between hemoglobin and metal ion. In other hand, when entering into animal body, metal ion interacts with protein following by change of protein structure and its function. In the present study, the interaction between transition metals (Co2+, Hg2+ and Ag+) and bovine hemoglobin was studied in vitro using UV spectrometry, fluorescence and circular dichroism techniques.The data from UV spectrometry demonstrated that Co2+ has a remarkable LMCT, whereas the LMCT of Hg2+ and Ag* were not clear. This result indicates the Co2+ binding induces a slow rearrangement of tertiary structure, which enhances Co2+ site on Hb. But Hg2+, Ag+ binding on Hb causes a fast rearrangement from the original conformation (in the absence of Hg2+ or Ag+ ion) to the final conformation (binding with Hg2+ or Ag+ ion). The intrinsic fluorescence spectra, shows that Co2+, Hg2+ and Ag+ affect tertiary and quaternary structure of Hb which is supported by the CD data in near-UV spectra and Soret CD spectra. The far-UV spectra and the quantitative amounts of α-helix, β-sheet and random coil secondary structure fractions show that the secondary structure was affected by the increasing helicity of the protein in the presence of Co2+ and Ag+, but the helicity of the protein decreases in the presence ofHg2+.The data obtained demonstrated that: the three metal ion affect secondary, tertiary and quaternary structure of Hb, and the difference on action of each metal on Hb structure suggest that the interaction mechanism between Hb and Co2+, Hg2+ and Ag+ differ from each metal ion to other.