TY - JOUR
T1 - Thermodynamics of carbon monoxide photodissociation from the fully reduced cytochrome aa3 oxidase from Rb. sphaeroides
AU - Miksovska, Jaroslava
AU - Gennis, Robert B.
AU - Larsen, Randy W.
N1 - Funding Information:
The Authors would like to thank the American Heart Association (AHA 025537 to RWL), the National Science Foundation (NSF MCB0317334 to RWL), and the Department of Energy (DE-FG02-87ER13716, RBG) for their support for this work.
PY - 2006/3
Y1 - 2006/3
N2 - Photodissociation of the fully reduced carbonmonoxy bound cytochrome aa3 from Rb. sphaeroides results in ultrafast ligand transfer between heme a3 and CuB, which is followed by thermal dissociation from CuB on longer time scales. We have utilized photoacoustic calorimetry to obtain a detailed thermodynamic description of the mechanism of ligand photodissociation and transfer between heme a3 and CuB. Subsequent to ligand photodissociation an additional process, which has not been characterized previously, was observed with the lifetime of 485 ns at 18 °C and is coupled to a volume expansion of 3.3 ml mol-1. From the temperature dependence, an activation barrier of 4 kcal mol-1 was determined. We attribute the observed 500 ns process to changes in CuB ligation subsequent to ligand translocation. In a photoacoustic study on CO photodissociation from bovine heart aa3 oxidase, no volume changes were observed on the ns timescale, indicating that a different mechanism may control ligand dissociation and binding within the binuclear center of the bacterial and bovine enzymes.
AB - Photodissociation of the fully reduced carbonmonoxy bound cytochrome aa3 from Rb. sphaeroides results in ultrafast ligand transfer between heme a3 and CuB, which is followed by thermal dissociation from CuB on longer time scales. We have utilized photoacoustic calorimetry to obtain a detailed thermodynamic description of the mechanism of ligand photodissociation and transfer between heme a3 and CuB. Subsequent to ligand photodissociation an additional process, which has not been characterized previously, was observed with the lifetime of 485 ns at 18 °C and is coupled to a volume expansion of 3.3 ml mol-1. From the temperature dependence, an activation barrier of 4 kcal mol-1 was determined. We attribute the observed 500 ns process to changes in CuB ligation subsequent to ligand translocation. In a photoacoustic study on CO photodissociation from bovine heart aa3 oxidase, no volume changes were observed on the ns timescale, indicating that a different mechanism may control ligand dissociation and binding within the binuclear center of the bacterial and bovine enzymes.
KW - CO photolysis
KW - Cytochrome c oxidase
KW - Photoacoustic calorimetry
KW - Respiratory protein
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U2 - 10.1016/j.bbabio.2006.01.008
DO - 10.1016/j.bbabio.2006.01.008
M3 - Article
C2 - 16545339
AN - SCOPUS:33646109553
SN - 0005-2728
VL - 1757
SP - 182
EP - 188
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
IS - 3
ER -