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Histidine E7 dynamics modulates ligand exchange between distal pocket and solvent in AHb1 from Arabidopsis thaliana

Posted November 16th, 2011 by xbarril
TitleHistidine E7 dynamics modulates ligand exchange between distal pocket and solvent in AHb1 from Arabidopsis thaliana
Publication TypeJournal Article
Year of Publication2011
AuthorsSpyrakis, F, Faggiano S, Abbruzzetti S, Dominici P, Cacciatori E, Astegno A, Droghetti E, Feis A, Smulevich G, Bruno S, Mozzarelli A, Cozzini P, Viappiani C, Bidon-Chanal A, Luque FJ
JournalThe journal of physical chemistry.B
Volume115
Issue14
Pagination4138 - 4146
Date Published2011/04/14/
KeywordsArabidopsis/metabolism; Arabidopsis Proteins/chemistry/genetics/metabolism; Hemoglobins/chemistry/genetics/metabolism; Histidine/chemistry; Kinetics; Ligands; Molecular Dynamics Simulation; Protein Structure, Raman, Tertiary; Recombinant Proteins/chemistry/genetics/metabolism; Solvents/chemistry; Spectrum Analysis
AbstractThe distal His residue in type 1 nonsymbiotic hemoglobin AHb1 from Arabidopsis thaliana plays a fundamental role in stabilizing the bound ligand. This residue might also be important in regulating the accessibility to the distal cavity. The feasibility of this functional role has been examined using a combination of experimental and computational methods. We show that the exchange of CO between the solvent and the reaction site is modulated by a swinging motion of the distal His, which opens a channel that connects directly the distal heme pocket with the solvent. The nearby PheB10 aids the distal His in the stabilization of the bound ligand by providing additional protection against solvation. Overall, these findings provide evidence supporting the functional implications of the conformational rearrangement found for the distal His in AHb1, which mimics the gating role proposed for the same residue in myoglobin.