title: 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.
authors.affiliation: Unité de RMN des Biomolécules, CNRS URA 2185, Institut Pasteur, 75015 Paris, France. ccaillet@pasteur.fr
authors.forename: Célia
authors.initials: C
authors.lastname: Caillet-Saguy
authors.forename: Paola
authors.initials: P
authors.lastname: Turano
authors.forename: Mario
authors.initials: M
authors.lastname: Piccioli
authors.forename: Gudrun S
authors.initials: GS
authors.lastname: Lukat-Rodgers
authors.forename: Mirjam
authors.initials: M
authors.lastname: Czjzek
authors.forename: Bruno
authors.initials: B
authors.lastname: Guigliarelli
authors.forename: Nadia
authors.initials: N
authors.lastname: Izadi-Pruneyre
authors.forename: Kenton R
authors.initials: KR
authors.lastname: Rodgers
authors.forename: Muriel
authors.initials: M
authors.lastname: Delepierre
authors.forename: Anne
authors.initials: A
authors.lastname: Lecroisey
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006418:Heme / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006639:Histidine / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020125:Mutation, Missense; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012706:Serratia marcescens / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; C093956:HasA protein, Serratia marcescens; D008565:Membrane Proteins; D006418:Heme; D006639:Histidine; D007501:Iron