Deciphering the Structural Role of Histidine 83 for Heme Binding in Hemophore HasA

• Published in: The Journal of biological chemistry Vol. 283; no. 9; pp. 5960 - 5970
• Main Authors: Caillet-Saguy, Célia, Turano, Paola, Piccioli, Mario, Lukat-Rodgers, Gudrun S., Czjzek, Mirjam, Guigliarelli, Bruno, Izadi-Pruneyre, Nadia, Rodgers, Kenton R., Delepierre, Muriel, Lecroisey, Anne
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 29.02.2008; American Society for Biochemistry and Molecular Biology
• Subjects: Bacterial Proteins; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biochemistry, Molecular Biology; Carrier Proteins; Carrier Proteins - chemistry; Carrier Proteins - genetics; Carrier Proteins - metabolism; Heme; Heme - chemistry; Heme - genetics; Heme - metabolism; Histidine; Histidine - chemistry; Histidine - genetics; Histidine - metabolism; Hydrogen-Ion Concentration; Iron; Iron - chemistry; Iron - metabolism; Life Sciences; Membrane Proteins; Membrane Proteins - chemistry; Membrane Proteins - genetics; Membrane Proteins - metabolism; Mutation, Missense; Protein Binding; Protein Structure, Tertiary; Serratia marcescens; Serratia marcescens - chemistry; Serratia marcescens - genetics; Serratia marcescens - metabolism; Structural Biology; Structure-Activity Relationship
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M703795200

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.