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Deciphering the structural role of histidine 83 for heme binding in hemophore HasA.

Abstract : Heme carrier HasA has a unique type of histidine/tyrosine heme iron ligation in which the iron ion is in a thermally driven two spin states equilibrium. We recently suggested that the H-bonding between Tyr75 and the invariantly conserved residue His83 modulates the strength of the iron-Tyr75 bond. To unravel the role of His83, we characterize the iron ligation and the electronic properties of both wild type and H83A mutant by a variety of spectroscopic techniques. Although His83 in wild type modulates the strength of the Tyr-iron bond, its removal causes detachment of the tyrosine ligand, thus giving rise to a series of pH-dependent equilibria among species with different axial ligation. The five coordinated species detected at physiological pH may represent a possible intermediate of the heme transfer mechanism to the receptor.
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Submitted on : Tuesday, March 3, 2009 - 2:17:20 PM
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Célia Caillet-Saguy, Paola Turano, Mario Piccioli, Gudrun S. Lukat-Rodgers, Mirjam Czjzek, et al.. Deciphering the structural role of histidine 83 for heme binding in hemophore HasA.. Journal of Biological Chemistry, American Society for Biochemistry and Molecular Biology, 2008, 283 (9), pp.5960-70. ⟨10.1074/jbc.M703795200⟩. ⟨pasteur-00365415⟩



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