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Kinetic studies of the reactions of O2 and NO with reduced Thermus thermophilus ba3 and bovine aa3 using photolabile carriers

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Show simple item record Einarsdóttira, Ólöf Funatogawaa, Chie Soulimane, Tewfik Szundia, Istvan 2019-10-31T14:29:58Z 2019-10-31T14:29:58Z 2012
dc.description peer-reviewed en_US
dc.description.abstract The reactions of molecular oxygen (O2) and nitric oxide (NO) with reduced Thermus thermophilus (Tt) ba3 and bovine heart aa3 were investigated by time-resolved optical absorption spectroscopy to establish possible relationships between the structural diversity of these enzymes and their reaction dynamics. To determine whether the photodissociated carbon monoxide (CO) in the CO flow-flash experiment affects the ligand binding dynamics, we monitored the reactions in the absence and presence of CO using photolabile O2 and NO complexes. The binding of O2/NO to reduced ba3 in the absence of CO occurs with a second-order rate constant of 1 × 109 M− 1 s− 1. This rate is 10-times faster than for the mammalian enzyme, and which is attributed to structural differences in the ligand channels of the two enzymes. Moreover, the O2/NO binding in ba3 is 10-times slower in the presence of the photodissociated CO while the rates are the same for the bovine enzyme. This indicates that the photodissociated CO directly or indirectly impedes O2 and NO access to the active site in Tt ba3, and that traditional CO flow-flash experiments do not accurately reflect the O2 and NO binding kinetics in ba3. We suggest that in ba3 the binding of O2 (NO) to heme a32 + causes rapid dissociation of CO from CuB+ through steric or electronic effects or, alternatively, that the photodissociated CO does not bind to CuB+. These findings indicate that structural differences between Tt ba3 and the bovine aa3 enzyme are tightly linked to mechanistic differences in the functions of these enzymes. This article is part of a Special Issue entitled: Respiratory Oxidases. en_US
dc.language.iso eng en_US
dc.publisher Elsevier en_US
dc.relation BICF685 en_US
dc.relation.ispartofseries Biochimica et Biophysica Acta (BBA) - Bioenergetics;1817 (4), pp. 672-679
dc.rights This is the author’s version of a work that was accepted for publication in Biochimica et Biophysica Acta (BBA) - Bioenergetics . Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2012, 1817 (4), pp. 672-679, en_US
dc.subject double-laser transient absorption spectroscopy en_US
dc.title Kinetic studies of the reactions of O2 and NO with reduced Thermus thermophilus ba3 and bovine aa3 using photolabile carriers en_US
dc.type info:eu-repo/semantics/article en_US
dc.type.supercollection all_ul_research en_US
dc.type.supercollection ul_published_reviewed en_US
dc.identifier.doi 10.1016/j.bbabio.2011.12.005
dc.contributor.sponsor National Institutes of Health Grants en_US
dc.contributor.sponsor SFI en_US
dc.relation.projectid GM53788 en_US
dc.relation.projectid BICF685 en_US
dc.rights.accessrights info:eu-repo/semantics/openAccess en_US

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