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

Célia Caillet-Saguy (1) , Paola Turano (1) , Mario Piccioli (1) , Gudrun S. Lukat-Rodgers (1) , Mirjam Czjzek (1) , Bruno Guigliarelli (1) , Nadia Izadi-Pruneyre (1) , Kenton R. Rodgers (1) , Muriel Delepierre (1) , Anne Lecroisey (1)

1 Résonance Magnétique Nucléaire des Biomolécules

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.

Domains: Structural Biology [q-bio.BM]

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, 2008, 283 (9), pp.5960-70. ⟨10.1074/jbc.M703795200⟩. ⟨pasteur-00365415⟩