Journal of Bioenergetics and Biomembranes 

About: Journal of Bioenergetics and Biomembranes is an academic journal published by Springer Science+Business Media. The journal publishes majorly in the area(s): Mitochondrion & ATP synthase. It has an ISSN identifier of 0145-479X. Over the lifetime, 2488 publications have been published receiving 100462 citations.

The Na,K-ATPase.

Abstract: The energy dependent exchange of cytoplasmic Na+ for extracellular K+ in mammalian cells is due to a membrane bound enzyme system, the Na,K-ATPase. The exchange sustains a gradient for Na+ into and for K+ out of the cell, and this is used as an energy source for creation of the membrane potential, for its de- and repolarisation, for regulation of cytoplasmic ionic composition and for transepithelial transport. The Na,K-ATPase consists of two membrane spanning polypeptides, an α-subunit of 112-kD and a β-subunit, which is a glycoprotein of 35-kD. The catalytic properties are associated with the α-subunit, which has the binding domain for ATP and the cations. In the review, attention will be given to the biochemical characterization of the reaction mechanism underlying the coupling between hydrolysis of the substate ATP and transport of Na+ and K+.

The inhibition of mitochondrial cytochrome oxidase by the gases carbon monoxide, nitric oxide, hydrogen cyanide and hydrogen sulfide: Chemical mechanism and physiological significance

Abstract: The four gases, nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H2S) and hydrogen cyanide (HCN) all readily inhibit oxygen consumption by mitochondrial cytochrome oxidase. This inhibition is responsible for much of their toxicity when they are applied externally to the body. However, recently these gases have all been implicated, to greater or lesser extents, in normal cellular signalling events. In this review we analyse the chemistry of this inhibition, comparing and contrasting mechanism and discussing physiological consequences. The inhibition by NO and CO is dependent on oxygen concentration, but that of HCN and H2S is not. NO and H2S are readily metabolised by oxidative processes within cytochrome oxidase. In these cases the enzyme may act as a physiological detoxifier of these gases. CO oxidation is much slower and unlikely to be as physiologically important. The evidence for normal physiological levels of these gases interacting with cytochrome oxidase is equivocal, in part because there is little robust data about their steady state concentrations. A reasonable case can be made for NO, and perhaps CO and H2S, inhibiting cytochrome oxidase in vivo, but endogenous levels of HCN seem unlikely to be high enough.

Recent progress on regulation of the mitochondrial permeability transition pore; a cyclosporin-sensitive pore in the inner mitochondrial membrane.

Abstract: The mitochondrial permeability transition pore allows solutes with a m.w. ≲1500 to equilibrate across the inner membrane. A closed pore is favored by cyclosporin A acting at a high-affinity site, which may be the matrix space cylophilin isozyme. Early results obtained with cyclosporin A analogs and metabolites support this hypothesis. Inhibition by cyclosporin does not appear to require inhibition of calcineurin activity; however, it may relate to inhibition of cyclophilin peptide bond isomerase activity. The permeability transition pore is strongly regulated by both the membrane potential (Δψ) and ΔpH components of the mitochondrial protonmotive force. A voltage sensor which is influenced by the disulfide/sulhydryl state of vicinal sulfhydryls is proposed to render pore opening sensitive to Δψ. Early results indicate that this sensor is also responsive to membrane surface potential and/or to surface potential gradients. Histidine residues located on the matrix side of the inner membrane render the pore responsive to ΔpH. The pore is also regulated by several ions and metabolites which act at sites that are interactive. There are many analogies between the systems which regulate the permeability transition pore and the NMDA receptor channel. These suggest structural similarities and that the permeability transition pore belongs to the family of ligand gated ion channels.

Lipoproteins in bacteria

Abstract: Covalent modification of membrane proteins with lipids appears to be ubiquitous in all living cells. The major outer membrane (Braun's) lipoprotein of E. coli, the prototype of bacterial lipoproteins, is first synthesized as a precursor protein. Analysis of signal sequences of 26 distinct lipoprotein precursors has revealed a consensus sequence of lipoprotein modification/processing site of Leu-(Ala, Ser)-(Gly, Ala)-Cys at -3 to +1 positions which would represent the cleavage region of about three-fourth of all lipoprotein signal sequences in bacteria. Unmodified prolipoprotein with the putative consensus sequence undergoes sequential modification and processing reactions catalyzed by glyceryl transferase, O-acyl transferase(s), prolipoprotein signal peptidase (signal peptidase II), and N-acyl transferase to form mature lipoprotein. Like all exported proteins, the export of lipoprotein requires functional SecA, SecY, and SecD proteins. Thus all precursor proteins are exported through a common pathway accessible to both signal peptidase I and signal peptidase II. The rapidly increasing list of lipid-modified proteins in both prokaryotic as well as eukaryotic cells indicates that lipoproteins comprise a diverse group of structurally and functionally distinct proteins. They share a common structural feature which is derived from a common biosynthetic pathway.

Mitochondrial oxygen radical generation and leak: sites of production in states 4 and 3, organ specificity, and relation to aging and longevity.

Abstract: Studies in heart and nonsynaptic brain mitochondria from two mammals and three birds show that complex I generates oxygen radicals in heart and nonsynaptic brain mitochondria in States 4 and 3, whereas complex III does it only in heart mitochondria and only in State 4. The increase in oxygen consumption during the State 4 to 3 transition is not accompanied by a proportional increase in oxygen radical generation. This will protect mitochondria and tissues during bursts of activity. Comparisons between young and old rodents do not show a consistent pattern of variation in mitochondrial oxygen radical production during aging. However, all the interspecies comparisons performed to date between different mammals, and between mammals and birds, agree that animals with high maximum longevities have low rates of mitochondrial oxygen radical production, irrespective of the value of their basal specific metabolic rate. The sites and mechanisms allowing this, the recently described low degree of membrane fatty acid unsaturation of longevous animals, and their relation to longevity and aging are discussed.