Molecular basis of the Bohr effect in arthropod hemocyanin.

The Journal of Biological Chemistry
Shun HirotaLuigi Bubacco

Abstract

Flash photolysis and K-edge x-ray absorption spectroscopy (XAS) were used to investigate the functional and structural effects of pH on the oxygen affinity of three homologous arthropod hemocyanins (Hcs). Flash photolysis measurements showed that the well-characterized pH dependence of oxygen affinity (Bohr effect) is attributable to changes in the oxygen binding rate constant, k(on), rather than changes in k(off). In parallel, coordination geometry of copper in Hc was evaluated as a function of pH by XAS. It was found that the geometry of copper in the oxygenated protein is unchanged at all pH values investigated, while significant changes were observed for the deoxygenated protein as a function of pH. The interpretation of these changes was based on previously described correlations between spectral lineshape and coordination geometry obtained for model compounds of known structure (Blackburn, N. J., Strange, R. W., Reedijk, J., Volbeda, A., Farooq, A., Karlin, K. D., and Zubieta, J. (1989) Inorg. Chem., 28, 1349-1357). A pH-dependent change in the geometry of cuprous copper in the active site of deoxyHc, from pseudotetrahedral toward trigonal was assigned from the observed intensity dependence of the 1s --> 4p(z) transition ...Continue Reading

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Citations

Apr 22, 2010·The Journal of Biological Chemistry·Shun HirotaLuigi Bubacco
Mar 5, 2014·Chemical Reviews·Edward I SolomonLi Tian
Apr 26, 2014·The Journal of Physical Chemistry. B·Toru Saito, Walter Thiel
Jul 6, 2014·Food Chemistry·Melanie J CekoHugh H Harris
Jan 26, 2013·The Journal of Experimental Biology·Christian DamsgaardRoy E Weber

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