The Fe(III) --> Fe(II) reduction of the heme iron in aquomet-myoglobin, induced by x-rays at cryogenics temperatures, produces a thermally trapped nonequilibrium state in which a water molecule is still bound to the iron. Water dissociates at T > 160 K, when the protein can relax toward its new equilibrium, deoxy form. Synchrotron radiation x-ray absorption spectroscopy provides information on both the redox state and the Fe-heme structure. Owing to the development of a novel method to analyze the low-energy region of x-ray absorption spectroscopy, we obtain structural pictures of this photo-inducible, irreversible process, with 0.02-0.06-A accuracy, on the protein in solution as well as in crystal. After photo-reduction, the iron-proximal histidine bond is shortened by 0.15 A, a reinforcement that should destabilize the iron in-plane position favoring water dissociation. Moreover, we are able to get the distance of the water molecule even after dissociation from the iron, with a 0.16-A statistical error.

Della Longa, S., Arcovito, A., Benfatto, M., Congiu Castellano, A., Girasole, M., Hazemann, J. L., Lo Bosco, A., Redox-induced structural dynamics of Fe-heme-ligand in myoglobin by X-ray Absorption Spectroscopy, <<BIOPHYSICAL JOURNAL>>, 2003; (86): 448-454 [http://hdl.handle.net/10807/6827]

Redox-induced structural dynamics of Fe-heme-ligand in myoglobin by X-ray Absorption Spectroscopy

Arcovito, Alessandro;
2003

Abstract

The Fe(III) --> Fe(II) reduction of the heme iron in aquomet-myoglobin, induced by x-rays at cryogenics temperatures, produces a thermally trapped nonequilibrium state in which a water molecule is still bound to the iron. Water dissociates at T > 160 K, when the protein can relax toward its new equilibrium, deoxy form. Synchrotron radiation x-ray absorption spectroscopy provides information on both the redox state and the Fe-heme structure. Owing to the development of a novel method to analyze the low-energy region of x-ray absorption spectroscopy, we obtain structural pictures of this photo-inducible, irreversible process, with 0.02-0.06-A accuracy, on the protein in solution as well as in crystal. After photo-reduction, the iron-proximal histidine bond is shortened by 0.15 A, a reinforcement that should destabilize the iron in-plane position favoring water dissociation. Moreover, we are able to get the distance of the water molecule even after dissociation from the iron, with a 0.16-A statistical error.
Inglese
Della Longa, S., Arcovito, A., Benfatto, M., Congiu Castellano, A., Girasole, M., Hazemann, J. L., Lo Bosco, A., Redox-induced structural dynamics of Fe-heme-ligand in myoglobin by X-ray Absorption Spectroscopy, <<BIOPHYSICAL JOURNAL>>, 2003; (86): 448-454 [http://hdl.handle.net/10807/6827]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10807/6827
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