An EPR Study of NO Bonding to Erythrocruorin from the Earthworm Octolasium Complanatum |
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| Authors: | Alessandro Desideri Emilia Chiancone Franca Ascoli |
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| Institution: | CNR Center of Molecular Biology, Institutes of Chemistry and Biochemistry, Faculty of Medicine, University of Rome “La Sapienza,” Italy;Department of Cell Biology, University of Camerino, Italy |
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| Abstract: | The EPR properties of the nitric oxide derivative of Octolasium complanatum erythrocruorin have been investigated as a function of the concentration of protons and cations which are known to affect the oxygen-linked allosteric equilibrium. The EPR spectrum has a rhombic shape with gx = 2.08, gz = 2.005, and gy = 1.99, and remains unchanged under all the experimental conditions used. A supernyperfine pattern consisting of nine equally spaced lines is present in the gz region indicating an interaction with two nonequivalent nitrogen atoms, one contributed by the nitric oxide and the other by the proximal histidine. The constancy of the EPR spectrum suggests that changes in the allosteric equilibrium do not involve differences in the strain of the Fe(II)-histidine bond as in tetrameric hemoglobins. |
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