Estimation of the H+/H- ratio of the reaction catalysed by the nicotinamide nucleotide transhydrogenase in chromatophores from over-expressing strains of Rhodospirillum rubrum and in liposomes inlaid with the purified bovine enzyme Journal Article


Author(s): Bizouarn, Tania; Sazanov, Leonid A; Aubourg, Sébastien; Jackson, Julie B
Article Title: Estimation of the H+/H- ratio of the reaction catalysed by the nicotinamide nucleotide transhydrogenase in chromatophores from over-expressing strains of Rhodospirillum rubrum and in liposomes inlaid with the purified bovine enzyme
Affiliation
Abstract: Two strains of Rhodospirillum rubrum were constructed in which, by a gene dosage effect, the transhydrogenase activity of isolated chromatophores was increased 7-10-fold and 15-20-fold, respectively. The H+/H- ratio (the ratio of protons translocated per hydride ion equivalent transferred from NADPH to an NAD+ analogue, acetyl pyridine adenine dinucleotide), determined by a spectroscopic technique, was approximately 1.0 for chromatophores from the over-expressing strains, but was only approximately 0.6 for wild-type chromatophores. Highly-coupled proteoliposomes were prepared containing purified transhydrogenase from beef-heart mitochondria. Using the same technique, the H+/H- ratio was close to 1.0 for these proteoliposomes. It is suggested that the mechanistic H+/H- ratio is indeed unity, but that a low ratio is obtained in wild-type chromatophores because of inhomogeneity in the vesicle population.
Keywords: Chromatophore; Hydride ion transfer; Liposome; Nicotinamide nucleotide transhydrogenase; Overexpression; Proton/hydride ratio
Journal Title: Biochimica et Biophysica Acta - Bioenergetics
Volume: 1273
Issue 1
ISSN: 0005-2728
Publisher: Elsevier  
Date Published: 1996-01-11
Start Page: 4
End Page: 12
DOI: 10.1016/0005-2728(95)00125-5
Open access: no