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Oxygen and nitric oxide rebinding kinetics in nonsymbiotic hemoglobin AHb1 from Arabidopsis thaliana
Author(s) -
Abbruzzetti Stefania,
Faggiano Serena,
Spyrakis Francesca,
Bruno Stefano,
Mozzarelli Andrea,
Astegno Alessandra,
Dominici Paola,
Viappiani Cristiano
Publication year - 2011
Publication title -
iubmb life
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.132
H-Index - 113
eISSN - 1521-6551
pISSN - 1521-6543
DOI - 10.1002/iub.546
Subject(s) - chemistry , photodissociation , kinetics , hemoglobin , flash photolysis , oxygen , nitric oxide , ligand (biochemistry) , stereochemistry , diatomic molecule , photochemistry , reaction rate constant , docking (animal) , biophysics , molecule , receptor , biochemistry , organic chemistry , biology , physics , quantum mechanics , medicine , nursing
Type 1 nonsymbiotic hemoglobin from Arabidopsis thaliana (AHb1) shows a partial bis‐histidyl hexacoordination but can reversibly bind diatomic ligands. The physiological function is still unclear, but the high oxygen affinity rules out a function related to O 2 sensing, carrying, or storing. To gain insight into its possible functional roles, we have investigated its O 2 and NO rebinding kinetics after laser flash photolysis. The rate constants of the rebinding from the primary docking site for both O 2 and NO are higher than CO, with lower photolysis yields. Moreover, the amplitude of the geminate phase increases and, as for CO, the numerical analysis of the experimental curves suggests the existence of an internal pathway leading, with high rate, to an additional docking site. However, the accessibility to this site seems to be strongly ligand‐dependent, being lower for O 2 and higher for NO. © 2011 IUBMB IUBMB Life, 63(12): 1094–1100, 2011