title: Histidine E7 dynamics modulates ligand exchange between distal pocket and solvent in AHb1 from Arabidopsis thaliana.
abstract: The 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.
authors.affiliation: Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Università degli Studi di Parma, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Spyrakis
authors.forename: Serena
authors.initials: S
authors.lastname: Faggiano
authors.forename: Stefania
authors.initials: S
authors.lastname: Abbruzzetti
authors.forename: Paola
authors.initials: P
authors.lastname: Dominici
authors.forename: Elena
authors.initials: E
authors.lastname: Cacciatori
authors.forename: Alessandra
authors.initials: A
authors.lastname: Astegno
authors.forename: Enrica
authors.initials: E
authors.lastname: Droghetti
authors.forename: Alessandro
authors.initials: A
authors.lastname: Feis
authors.forename: Giulietta
authors.initials: G
authors.lastname: Smulevich
authors.forename: Stefano
authors.initials: S
authors.lastname: Bruno
authors.forename: Andrea
authors.initials: A
authors.lastname: Mozzarelli
authors.forename: Pietro
authors.initials: P
authors.lastname: Cozzini
authors.forename: Cristiano
authors.initials: C
authors.lastname: Viappiani
authors.forename: A
authors.initials: A
authors.lastname: Bidon-Chanal
authors.forename: F Javier
authors.initials: FJ
authors.lastname: Luque
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006454:Hemoglobins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006639:Histidine / Q000737:chemistry*; D007700:Kinetics; D008024:Ligands; D056004:Molecular Dynamics Simulation; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012997:Solvents / Q000737:chemistry*; D013059:Spectrum Analysis, Raman
chemical_list: C470347:AHB1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D006454:Hemoglobins; D008024:Ligands; D011994:Recombinant Proteins; D012997:Solvents; D006639:Histidine