Cytoglobin is a recently discovered hexa-co-ordinate haemoglobin that does not appear to function as a classical oxygen-binding protein. Its function is unknown and studies on the effects of changes in its expression have not decisively determined its role within the cell. In the present paper, we report that the protein is transformed from hexa-co-ordinate to penta-co-ordinate on binding a lipid molecule. This transformation occurs with the ferric oxidation state of the protein, but not the ferrous state, indicating that this process only occurs under an oxidative environment and may thus be related to redox-linked cell signalling mechanisms. Oleate binds to the protein in a 1:1 stoichiometry and with high affinity (Kd=0.7 μM); however, stopped-flow kinetic measurements yield a Kd value of 110 μM. The discrepancy between these Kd values may be rationalized by recognizing that cytoglobin is a disulfide-linked dimer and invoking co-operativity in oleate binding. The lipid-induced transformation of cytoglobin from hexa-co-ordinate to penta-co-ordinate does not occur with similar hexa-co-ordinate haemoglobins such as neuroglobin, and therefore appears to be a unique property of cytoglobin among the haemoglobin superfamily. The lipid-derived transformation may explain why cytoglobin has enhanced peroxidatic activity, converting lipids into various oxidized products, a property virtually absent from neuroglobin and much decreased in myoglobin. We propose that the binding of ferric cytoglobin to lipids and their subsequent transformation may be integral to the physiological function of cytoglobin, generating cell signalling lipid molecules under an oxidative environment.
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Research Article|
February 24 2011
Lipid binding to cytoglobin leads to a change in haem co-ordination: a role for cytoglobin in lipid signalling of oxidative stress
Brandon J. Reeder
;
Brandon J. Reeder
1
1Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, U.K.
1To whom correspondence should be addressed (email reedb@essex.ac.uk).
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Dimitri A. Svistunenko
;
Dimitri A. Svistunenko
1Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, U.K.
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Michael T. Wilson
Michael T. Wilson
1Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, U.K.
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Biochem J (2011) 434 (3): 483–492.
Article history
Received:
July 28 2010
Revision Received:
December 16 2010
Accepted:
December 20 2010
Accepted Manuscript online:
December 20 2010
Citation
Brandon J. Reeder, Dimitri A. Svistunenko, Michael T. Wilson; Lipid binding to cytoglobin leads to a change in haem co-ordination: a role for cytoglobin in lipid signalling of oxidative stress. Biochem J 15 March 2011; 434 (3): 483–492. doi: https://doi.org/10.1042/BJ20101136
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