F1 and F0 connections in the bovine mitochondrial ATP synthase: the role of the of alpha subunit N-terminus, oligomycin-sensitivity conferring protein (OCSP) and subunit d

Differential Expression ESTs Associated with Fluorosis in Rats Liver

The fluoride has volcanic activity and abundantly exists in environment combining with other elements as fluoride compounds. Recent researches indicated that the molecular mechanisms of intracellular fluoride toxicity were very complex. However, the molecular mechanisms underlying the effects on gene expression of chronic fluoride-induced damage is unknown, especially the detailed regulatory process of mitochondria. In the present study, we screened the differential expression ESTs associated with fluorosis by DDRT-PCR in rat liver. We gained 8 genes, 3 new ESTs, and 1 unknown function sequence and firstly demonstrated that microsomal glutathione S-transferase 1 (MGST1), ATP synthase H⁺ transporting mitochondrial F₀ complex subunit C1, selenoprotein S, mitochondrial IF1 protein, and mitochondrial succinyl-CoA synthetase alpha subunit were participated in mitochondria metabolism, functional and structural damage process caused by chronic fluorosis. This information will be very helpful for understanding the molecular mechanisms of fluorosis.

Iron transport by proteoliposomes containing mitochondrial F(1)F(0) ATP synthase isolated from rat heart

In this work, we present evidence of Fe(2+) transport by rat heart mitochondrial F(1)F(0) ATP synthase. Iron uptake by the vesicles containing the enzyme was concentration- and temperature-dependent, with an optimum temperature of 37 degrees C. Both ATP and ADP stimulated iron uptake in a concentration-dependent manner, whereas AMP, AMPPCP, and mADP did not. Inhibitors of the enzyme, oligomycin, and resveratrol similarly blocked iron transport. The iron uptake was confirmed by inhibition using specific antibodies against the alpha, beta, and c subunits of the enzyme. Interestingly, slight transport of common divalent and trivalent metal ions such as Mg(+2), Ca(+2), Mn(+2), Zn(+2), Cu(+2), Fe(+3), and Al(+3) was observed. Moreover, Cu(+2), even in the nM range, inhibited iron uptake and attained maximum inhibition of approximately 56%. Inorganic phosphate (Pi) in the medium exerted an opposite effect depending on the type of adenosine nucleotide, which was suppressed with ATP, but enhanced with ADP. A similarly stimulating effect of ATP and ADP with an inverse effect of Pi suggests that the activity of ATPase and ATP synthase may be associated with iron uptake in a different manner, probably via antiport of H(+).

The alpha/beta interfaces of alpha(1)beta(1), alpha(3)beta(3), and F1: domain motions and elastic energy stored during gamma rotation

ATP synthase (F(o)F(1)) consists of F(1) (ATP-driven motor) and F(o) (H(+)-driven motor). F(1) is a complex of alpha(3)beta(3)gammadeltaepsilon subunits, and gamma is the rotating cam in alpha(3)beta(3). Thermophilic F(1) (TF(1)) is exceptional in that it can be crystallized as a beta monomer and an alpha(3)beta(3) oligomer, and it is sufficiently stable to allow alphabeta refolding and reassembly of hybrid complexes containing 1, 2, and 3 modified alpha or beta. The nucleotide-dependent open-close conversion of conformation is an inherent property of an isolated beta and energy and signals are transferred through alpha/beta interfaces. The catalytic and noncatalytic interfaces of both mitochondrial F(1) (MF(1)) and TF(1) were analyzed by an atom search within the limits of 0.40 nm across the alphabeta interfaces. Seven (plus thermophilic loop in TF(1)) contact areas are located at both the catalytic and noncatalytic interfaces on the open beta form. The number of contact areas on closed beta increased to 11 and 9, respectively, in the catalytic and noncatalytic interfaces. The interfaces in the barrel domain are immobile. The torsional elastic strain applied through the mobile areas is concentrated in hinge residues and the P-loop in beta. The notion of elastic energy in F(o)F(1) has been revised. X-ray crystallography of F(1) is a static snap shot of one state and the elastic hypotheses are still inconsistent with the structure, dyamics, and kinetics of F(o)F(1). The domain motion and elastic energy in F(o)F(1) will be elucidated by time-resolved crystallography.

Regulation of the F1F0-ATP synthase rotary nanomotor in its monomeric-bacterial and dimeric-mitochondrial forms

The F(1)F(0)-adenosine triphosphate (ATP) synthase rotational motor synthesizes most of the ATP required for living from adenosine diphosphate, Pi, and a proton electrochemical gradient across energy-transducing membranes of bacteria, chloroplasts, and mitochondria. However, as a reversible nanomotor, it also hydrolyzes ATP during de-energized conditions in all energy-transducing systems. Thus, different subunits and mechanisms have emerged in nature to control the intrinsic rotation of the enzyme to favor the ATP synthase activity over its opposite and commonly wasteful ATPase turnover. Recent advances in the structural analysis of the bacterial and mitochondrial ATP synthases are summarized to review the distribution and mechanism of the subunits that are part of the central rotor and regulate its gyration. In eubacteria, the epsilon subunit works as a ratchet to favor the rotation of the central stalk in the ATP synthase direction by extending and contracting two alpha-helixes of its C-terminal side and also by binding ATP with low affinity in thermophilic bacteria. On the other hand, in bovine heart mitochondria, the so-called inhibitor protein (IF(1)) interferes with the intrinsic rotational mechanism of the central gamma subunit and with the opening and closing of the catalytic beta-subunits to inhibit its ATPase activity. Besides its inhibitory role, the IF(1) protein also promotes the dimerization of the bovine and rat mitochondrial enzymes, albeit it is not essential for dimerization of the yeast F(1)F(0) mitochondrial complex. High-resolution electron microscopy of the dimeric enzyme in its bovine and yeast forms shows a conical shape that is compatible with the role of the ATP synthase dimer in the formation of tubular the cristae membrane of mitochondria after further oligomerization. Dimerization of the mitochondrial ATP synthase diminishes the rotational drag of the central rotor that would decrease the coupling efficiency between rotation of the central stalk and ATP synthesis taking place at the F(1) portion. In addition, F(1)F(0) dimerization and its further oligomerization also increase the stability of the enzyme to natural or experimentally induced destabilizing conditions.

Structural and functional characterization of F(o)F(1)-ATP synthase on the extracellular surface of rat hepatocytes

Extracellular ATP formation from ADP and inorganic phosphate, attributed to the activity of a cell surface ATP synthase, has so far only been reported in cultures of some proliferating and tumoral cell lines. We now provide evidence showing the presence of a functionally active ecto-F(o)F(1)-ATP synthase on the plasma membrane of normal tissue cells, i.e. isolated rat hepatocytes. Both confocal microscopy and flow cytometry analysis show the presence of subunits of F(1) (alpha/beta and gamma) and F(o) (F(o)I-PVP(b) and OSCP) moieties of ATP synthase at the surface of rat hepatocytes. This finding is confirmed by immunoblotting analysis of the hepatocyte plasma membrane fraction. The presence of the inhibitor protein IF(1) is also detected on the hepatocyte surface. Activity assays show that the ectopic-ATP synthase can work both in the direction of ATP synthesis and hydrolysis. A proton translocation assay shows that both these mechanisms are accompanied by a transient flux of H(+) and are inhibited by F(1) and F(o)-targeting inhibitors. We hypothesise that ecto-F(o)F(1)-ATP synthase may control the extracellular ADP/ATP ratio, thus contributing to intracellular pH homeostasis.

Mutations in the Atp1p and Atp3p subunits of yeast ATP synthase differentially affect respiration and fermentation in Saccharomyces cerevisiae

ATP1-111, a suppressor of the slow-growth phenotype of yme1Delta lacking mitochondrial DNA is due to the substitution of phenylalanine for valine at position 111 of the alpha-subunit of mitochondrial ATP synthase (Atp1p in yeast). The suppressing activity of ATP1-111 requires intact beta (Atp2p) and gamma (Atp3p) subunits of mitochondrial ATP synthase, but not the stator stalk subunits b (Atp4p) and OSCP (Atp5p). ATP1-111 and other similarly suppressing mutations in ATP1 and ATP3 increase the growth rate of wild-type strains lacking mitochondrial DNA. These suppressing mutations decrease the growth rate of yeast containing an intact mitochondrial chromosome on media requiring oxidative phosphorylation, but not when grown on fermentable media. Measurement of chronological aging of yeast in culture reveals that ATP1 and ATP3 suppressor alleles in strains that contain mitochondrial DNA are longer lived than the isogenic wild-type strain. In contrast, the chronological life span of yeast cells lacking mitochondrial DNA and containing these mutations is shorter than that of the isogenic wild-type strain. Spore viability of strains bearing ATP1-111 is reduced compared to wild type, although ATP1-111 enhances the survival of spores that lacked mitochondrial DNA.

Correlation of mitochondrial protein expression in complexes I to V with natural and induced forms of canine idiopathic dilated cardiomyopathy

OBJECTIVE

To identify qualitative and quantitative differences in cardiac mitochondrial protein expression in complexes I to V between healthy dogs and dogs with natural or induced dilated cardiomyopathy (DCM).

SAMPLE POPULATION

Left ventricle samples were obtained from 7 healthy dogs, 7 Doberman Pinschers with naturally occurring DCM, and 7 dogs with DCM induced by rapid right ventricular pacing.

PROCEDURES

Fresh and frozen mitochondrial fractions were isolated from the left ventricular free wall and analyzed by 2-dimensional electrophoresis. Protein spots that increased or decreased in density by 2-fold or greater between groups were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry or quadrupole selecting, quadrupole collision cell, time-of-flight mass spectrometry.

RESULTS

A total of 22 altered mitochondrial proteins were identified in complexes I to V. Ten and 12 were found in complex I and complexes II to V, respectively. Five were mitochondrial encoded, and 17 were nuclear encoded. Most altered mitochondrial proteins in tissue specimens from dogs with naturally occurring DCM were associated with complexes I and V, whereas in tissue specimens from dogs subjected to rapid ventricular pacing, complexes I and IV were more affected. In the experimentally induced form of DCM, only nuclear-encoded subunits were changed in complex I. In both disease groups, the 22-kd subunit was downregulated.

CONCLUSIONS AND CLINICAL RELEVANCE

Natural and induced forms of DCM resulted in altered mitochondrial protein expression in complexes I to V. However, subcellular differences between the experimental and naturally occurring forms of DCM may exist.

cDNA representational difference analysis of ileal Peyer’s patches in lambs after oral inoculation with scrapie

cDNA representational difference analysis (RDA) was used to study gene expression profiles in the ileal Peyer's patch of a lamb 1 week after oral inoculation with the scrapie agent. Twenty-five differentially expressed cDNA fragments were identified and cloned. Sequence analysis indicated seven novel gene sequences. Other clones shared sequence homology with genes encoding ribosomal and mitochondrial proteins, the translation initiation factor EIF4GII and the bovine pancreatic thread protein. Reverse Northern was used to confirm the differential expression in another four lambs inoculated with scrapie and the tissue distribution of the novel genes was examined using Northern blot analysis.

FRET reveals changes in the F1–stator stalk interaction during activity of F1F0-ATP synthase

A stator is proposed as necessary to prevent futile rotation of the F(1) catalytic sector of mitochondrial ATP synthase (mtATPase) during periods of ATP synthesis or ATP hydrolysis. Although the second stalk of mtATPase is generally believed to fulfil the role of a stator capable of withstanding the stress produced by rotation of the central rotor, there is little evidence to directly support this view. We show that interaction between two candidate proteins of the second stalk, OSCP and subunit b, fused at their C-termini to GFP variants and assembled into functional mtATPase can be monitored in mitochondria using fluorescence resonance energy transfer (FRET). Substitution of native OSCP with a variant containing a glycine 166 to asparagine (G166N) substitution yielded a metastable complex. In contrast to the enzyme containing native OSCP, FRET could be irreversibly lowered for the enzyme containing G166N at a rate that correlated closely with the rate of enzyme activity (ATP hydrolysis). The non-hydrolysable ATP analogue, AMP-PCP did not have this effect. We conclude that two candidate proteins of the stator stalk, OSCP and b, are subject to stresses during enzyme catalytic activity commensurate with their role as a part of a stator stalk.

The structural and functional connection between the catalytic and proton translocating sectors of the mitochondrial F1F0-ATP synthase

The structural and functional connection between the peripheral catalytic F1 sector and the proton-translocating membrane sector F0 of the mitochondrial ATP synthase is reviewed. The observations examined show that the N-terminus of subunit gamma, the carboxy-terminal and central region of F0I-PVP(b), OSCP, and part of subunit d constitute a continuous structure, the lateral stalk, which connects the peripheries of F1 to F0 and surrounds the central element of the stalk, constituted by subunits gamma and delta. The ATPase inhibitor protein (IF1) binds at one side of the F1F0 connection. The carboxy-terminal segment of IF1 apparently binds to OSCP. The 42L-58K segment of IF1, which is per se the most active domain of the protein, binds at the surface of one of the three alpha/beta pairs of F1, thus preventing the cyclic interconversion of the catalytic sites required for ATP hydrolysis.