Structures and interactions of proteins involved in the coupling function of the protonmotive F(o)F(1)-ATP synthase

F1 ATP synthase β subunit is a putative receptor involved in white spot syndrome virus infection in shrimp by binding with viral envelope proteins VP51B and VP150

White spot syndrome virus (WSSV) is highly virulent toward shrimp, and F1 ATP synthase β subunit (ATPsyn-β) has been suggested to be involved in WSSV infection. Therefore, in this study, interactions between Penaeus monodon ATPsyn-β (PmATPsyn-β) and WSSV structural proteins were characterized. Based on the results of yeast two-hybrid, co-immunoprecipitation, and protein pull-down assays, WSSV VP51B and VP150 were identified as being able to interact with PmATPsyn-β. Membrane topology assay results indicated that VP51B and VP150 are envelope proteins with large portions exposed outside the WSSV virion. Cellular localization assay results demonstrated that VP51B and VP150 co-localize with PmATPsyn-β on the membranes of transfected cells. Enzyme-linked immunosorbent assay (ELISA) and competitive ELISA results demonstrated that VP51B and VP150 bound to PmATPsyn-β in a dose-dependent manner, which could be competitively inhibited by the addition of WSSV virions. In vivo neutralization assay results further showed that both recombinant VP51B and VP150 could delay mortality in shrimp challenged with WSSV.

Targeting breast cancer metabolism with a novel inhibitor of mitochondrial ATP synthesis

Inhibitors of mitochondrial respiration and ATP synthesis may promote the selective killing of respiration-competent cancer cells that are critical for tumor progression. We previously reported that CADD522, a small molecule inhibitor of the RUNX2 transcription factor, has potential for breast cancer treatment. In the current study, we show that CADD522 inhibits mitochondrial oxidative phosphorylation by decreasing the mitochondrial oxygen consumption rate (OCR) and ATP production in human breast cancer cells in a RUNX2-independent manner. The enzyme activity of mitochondrial ATP synthase was inhibited by CADD522 treatment. Importantly, results from cellular thermal shift assays that detect drug-induced protein stabilization revealed that CADD522 interacts with both α and β subunits of the F1-ATP synthase complex. Differential scanning fluorimetry also demonstrated interaction of α subunits of the F1-ATP synthase to CADD522. These results suggest that CADD522 might target the enzymatic F1 subunits in the ATP synthase complex. CADD522 increased the levels of intracellular reactive oxygen species (ROS), which was prevented by MitoQ, a mitochondria-targeted antioxidant, suggesting that cancer cells exposed to CADD522 may elevate ROS from mitochondria. CADD522-increased mitochondrial ROS levels were enhanced by exogenously added pro-oxidants such as hydrogen peroxide or tert-butyl hydroperoxide. Conversely, CADD522-mediated cell growth inhibition was blocked by N-acetyl-l-cysteine, a general ROS scavenger. Therefore, CADD522 may exert its antitumor activity by increasing mitochondrial driven cellular ROS levels. Collectively, our data suggest in vitro proof-of-concept that supports inhibition of mitochondrial ATP synthase and ROS generation as contributors to the effectiveness of CADD522 in suppression of tumor growth.

Research review on the pharmacological effects of astragaloside IV

Astragalus membranaceus Bunge has been used to treat numerous diseases for thousands of years. As the main active substance of Astragalus membranaceus Bunge, astragaloside IV (AS-IV) also demonstrates the potent protective effect on focal cerebral ischemia/reperfusion, cardiovascular disease, pulmonary disease, liver fibrosis, and diabetic nephropathy. Based on studies published during the past several decades, the current state of AS-IV research and the pharmacological effects are detailed, elucidated, and summarized. This review systematically summarizes the pharmacological effects, metabolism mechanism, and the toxicity of AS-IV. AS-IV has multiple pharmacologic effects, including anti-inflammatory, antifibrotic, antioxidative stress, anti-asthma, antidiabetes, immunoregulation, and cardioprotective effect via numerous signaling pathways. According to the existing studies and clinical practices, AS-IV possesses potential for broad application in many diseases.

Optimization of ATP synthase function in mitochondria and chloroplasts via the adenylate kinase equilibrium

The bulk of ATP synthesis in plants is performed by ATP synthase, the main bioenergetics engine of cells, operating both in mitochondria and in chloroplasts. The reaction mechanism of ATP synthase has been studied in detail for over half a century; however, its optimal performance depends also on the steady delivery of ATP synthase substrates and the removal of its products. For mitochondrial ATP synthase, we analyze here the provision of stable conditions for (i) the supply of ADP and Mg(2+), supported by adenylate kinase (AK) equilibrium in the intermembrane space, (ii) the supply of phosphate via membrane transporter in symport with H(+), and (iii) the conditions of outflow of ATP by adenylate transporter carrying out the exchange of free adenylates. We also show that, in chloroplasts, AK equilibrates adenylates and governs Mg(2+) contents in the stroma, optimizing ATP synthase and Calvin cycle operation, and affecting the import of inorganic phosphate in exchange with triose phosphates. It is argued that chemiosmosis is not the sole component of ATP synthase performance, which also depends on AK-mediated equilibrium of adenylates and Mg(2+), adenylate transport, and phosphate release and supply.

The serum- and glucocorticoid-induced protein kinase-1 (Sgk-1) mitochondria connection: identification of the IF-1 inhibitor of the F(1)F(0)-ATPase as a mitochondria-specific binding target and the stress-induced mitochondrial localization of endogenous Sgk-1

The expression, localization and activity of the serum- and glucocorticoid-induced protein kinase, Sgk-1, are regulated by multiple hormonal and environmental cues including cellular stress. Biochemical fractionation and indirect immunofluorescence demonstrated that sorbitol induced hyperosmotic stress stimulated expression and triggered the localization of endogenous Sgk-1 into the mitochondria of NMuMG mammary epithelial cells. The immunofluorescence pattern of endogenous Sgk-1 was similar to that of a green fluorescent linked fusion protein linked to the N-terminal Sgk-1 fragment that encodes the mitochondrial targeting signal. In the presence or absence of cellular stress, exogenously expressed wild type Sgk-1 efficiently compartmentalized into the mitochondria demonstrating the mitochondrial import machinery per se is not stressed regulated. Co-immunoprecipitation and GST-pull down assays identified the IF-1 mitochondrial matrix inhibitor of the F1F0-ATPase as a new Sgk-1 binding partner, which represents the first observed mitochondrial target of Sgk-1. The Sgk-1/IF-1 interaction requires the 122-176 amino acid region within the catalytic domain of Sgk-1 and is pH dependent, occurring at neutral pH but not at slightly acidic pH, which suggests that this interaction is dependent on mitochondrial integrity. An in vitro protein kinase assay showed that the F1F0-ATPase can be directly phosphorylated by Sgk-1. Taken together, our results suggest that stress-induced Sgk-1 localizes to the mitochondria, which permits access to physiologically appropriate mitochondrial interacting proteins and substrates, such as IF-1 and the F1F0-ATPase, as part of the cellular stressed induced program.

QiShenYiQi Pills, a Compound Chinese Medicine, Ameliorates Doxorubicin-Induced Myocardial Structure Damage and Cardiac Dysfunction in Rats

QiShenYiQi Pills (QSYQ) is a compound Chinese medicine used for treatment of cardiovascular diseases. The present study investigated the effects of QSYQ on the Doxorubicin- (DOX-) induced disorders in rat cardiac structure and function and the possible mechanism underlying. A total of 24 male Sprague-Dawley rats were administrated by intraperitoneal injections with DOX at a dose of 2.5 mg/kg, once every day for a total of 6 times. After the 6th injection, the rats were evaluated by echocardiographic analysis, and the animals with injured heart (n = 14) were divided into 2 groups and further treated with (n = 7) or without (n = 7) QSYQ by gavage at a dose of 0.2 g/day, once a day, over the next 2 weeks. Two weeks after QSYQ treatment, the following variables were assessed: myocardial blood flow (MBF) by Laser-Doppler Perfusion Imager, the ratio of heart weight to body weight (HW/BW), myocardial histology, myocardial content of ATP, AMP, free fatty acids (FFAs) and AMP/ATP by ELISA, and expression of PPARα, PGC-1α, and ATP 5D by Western blot. Statistical analysis was performed using one-way ANOVA followed by Turkey test for multiple comparisons. DOX challenge significantly increased left ventricular internal diameter and HW/BW and decreased the thickness of the left ventricular posterior wall, the left ventricle ejection fraction, and the left ventricle fractional shortening. DOX also increased AMP, FFA, and AMP/ATP, decreased ATP, and downregulated the protein content of ATP 5D, PPAR α, and PGC-1 α. All these DOX-induced cardiac insults were attenuated significantly by QSYQ treatment. These results show the potential of QSYQ to ameliorate DOX-induced disorders in cardiac structure and function; this effect may be related to the increase in myocardial ATP content via the upregulation of ATP 5D, PPAR α, and PGC-1 α and the oxidation of FFA.

Modulation of the protein kinase Cdelta interaction with the "d" subunit of F1F0-ATP synthase in neonatal cardiac myocytes: development of cell-permeable, mitochondrially targeted inhibitor and facilitator peptides

The F(1)F(0)-ATP synthase provides approximately 90% of cardiac ATP, yet little is known regarding its regulation under normal or pathological conditions. Previously, we demonstrated that protein kinase Cdelta (PKCdelta) inhibits F(1)F(0) activity via an interaction with the "d" subunit of F(1)F(0)-ATP synthase (dF(1)F(0)) in neonatal cardiac myocytes (NCMs) (Nguyen, T., Ogbi, M., and Johnson, J. A. (2008) J. Biol. Chem. 283, 29831-29840). We have now identified a dF(1)F(0)-derived peptide (NH(2)-(2)AGRKLALKTIDWVSF(16)-COOH) that inhibits PKCdelta binding to dF(1)F(0) in overlay assays. We have also identified a second dF(1)F(0)-derived peptide (NH(2)-(111)RVREYEKQLEKIKNMI(126)-COOH) that facilitates PKCdelta binding to dF(1)F(0). Incubation of NCMs with versions of these peptides containing HIV-Tat protein transduction and mammalian mitochondrial targeting sequences resulted in their delivery into mitochondria. Preincubation of NCMs, with 10 nm extracellular concentrations of the mitochondrially targeted PKCdelta-dF(1)F(0) interaction inhibitor, decreased 100 nm 4beta-phorbol 12-myristate 13-acetate (4beta-PMA)-induced co-immunoprecipitation of PKCdelta with dF(1)F(0) by 50 +/- 15% and abolished the 30 nm 4beta-PMA-induced inhibition of F(1)F(0)-ATPase activity. A scrambled sequence (inactive) peptide, which contained HIV-Tat and mitochondrial targeting sequences, was without effect. In contrast, the cell-permeable, mitochondrially targeted PKCdelta-dF(1)F(0) facilitator peptide by itself induced the PKCdelta-dF(1)F(0) co-immunoprecipitation and inhibited F(1)F(0)-ATPase activity. In in vitro PKC add-back experiments, the PKCdelta-F(1)F(0) inhibitor blocked PKCdelta-mediated inhibition of F(1)F(0)-ATPase activity, whereas the facilitator induced inhibition. We have developed the first cell-permeable, mitochondrially targeted modulators of the PKCdelta-dF(1)F(0) interaction in NCMs. These novel peptides will improve our understanding of cardiac F(1)F(0) regulation and may have potential as therapeutics to attenuate cardiac injury.

Attenuation of the hypoxia-induced protein kinase Cdelta interaction with the 'd' subunit of F1Fo-ATP synthase in neonatal cardiac myocytes: implications for energy preservation and survival

The F1Fo-ATP synthase provides most of the heart's energy, yet events that alter its function during injury are poorly understood. Recently, we described a potent inhibitory effect on F1Fo-ATP synthase function mediated by the interaction of PKCdelta (protein kinase Cdelta) with dF1Fo ('d' subunit of the F1Fo-ATPase/ATP synthase). We have now developed novel peptide modulators which facilitate or inhibit the PKCdelta-dF1Fo interaction. These peptides include HIV-Tat (transactivator of transcription) protein transduction and mammalian mitochondrial-targeting sequences. Pre-incubation of NCMs (neonatal cardiac myocyte) with 10 nM extracellular concentrations of the mitochondrial-targeted PKCdelta-dF1Fo interaction inhibitor decreased Hx (hypoxia)-induced co-IP (co-immunoprecipitation) of PKCdelta with dF1Fo by 40+/-9%, abolished Hx-induced inhibition of F1Fo-ATPase activity, attenuated Hx-induced losses in F1Fo-derived ATP and protected against Hx- and reperfusion-induced cell death. A scrambled-sequence (inactive) peptide, which contained HIV-Tat and mitochondrial-targeting sequences, was without effect. In contrast, the cell-permeant mitochondrial-targeted PKCdelta-dF1Fo facilitator peptide, which we have shown previously to induce the PKCdelta-dF1Fo co-IP, was found to inhibit F1Fo-ATPase activity to an extent similar to that caused by Hx alone. The PKCdelta-dF1Fo facilitator peptide also decreased ATP levels by 72+/-18% under hypoxic conditions in the presence of glycolytic inhibition. None of the PKCdelta-dF1Fo modulatory peptides altered the inner mitochondrial membrane potential. Our studies provide the first evidence that disruption of the PKCdelta-dF1Fo interaction using cell-permeant mitochondrial-targeted peptides attenuates cardiac injury resulting from prolonged oxygen deprivation.

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(+).

Assessment of ProteoExtract subcellular fractionation kit reveals limited and incomplete enrichment of nuclear subproteome from frozen liver and heart tissue

The nuclear fraction of the ProteoExtract subcellular fractionation kit was assessed using frozen rat liver and heart tissue. Fractionation was evaluated by Western blot using protein markers for various subcellular compartments and followed up with LC/MS/MS analysis of the nuclear fractions. Of the proteins identified, nuclear proteins were in the minority (less than 15%) and there was poor representation of the various nuclear substructures when compared with liver nuclear isolations using a classical density-based centrifugation protocol. The ProteoExtract kit demonstrated poor specificity for the nucleus and offers limited promise for proteomics investigations of the nuclear subproteome in frozen tissue samples.

Pharmacological profile of the selective mitochondrial F1F0 ATP hydrolase inhibitor BMS-199264 in myocardial ischemia

The mitochondrial F1F0 ATP synthase is responsible for the majority of ATP production in mammals and does this through a rotary catalytic mechanism. Studies show that the F1F0 ATP synthase can switch to an ATP hydrolase, and this occurs under conditions seen during myocardial ischemia. This ATP hydrolysis causes wasting of ATP that does not produce work. The degree of ATP inefficiently hydrolyzed during ischemia may be as high as 50-90% of the total. A naturally occurring, reversible inhibitor (IF-1) of the hydrolase activity is in the mitochondria, and it has a pH optimum of 6.8. Based on studies with the nonselective (inhibit both synthase and hydrolase activity) inhibitors aurovertin B and oligomycin B reduce the rate of ATP depletion during ischemia, showing that IF-1 does not completely block hydrolase activity. Oligomycin and aurovertin cannot be used for treating myocardial ischemia as they will reduce ATP production in healthy tissue. We generated a focused structure-activity relationship, and several compounds were identified that selectively inhibited the F1F0 ATP hydrolase activity while having no effect on synthase function. One compound, BMS-199264 had no effect on F1F0 ATP synthase function in submitochondrial particles while inhibiting hydrolase function, unlike oligomycin that inhibits both. BMS-199264 selectively inhibited ATP decline during ischemia while not affecting ATP production in normoxic and reperfused hearts. BMS-191264 also reduced cardiac necrosis and enhanced the recovery of contractile function following reperfusion. These data also suggest that the reversal of the synthase and hydrolase activities is not merely a chemical reaction run in reverse.

Delta protein kinase C interacts with the d subunit of the F1F0 ATPase in neonatal cardiac myocytes exposed to hypoxia or phorbol ester. Implications for F1F0 ATPase regulation

Mitochondrial protein kinase C isozymes have been reported to mediate both cardiac ischemic preconditioning and ischemia/reperfusion injury. In addition, cardiac preconditioning improves the recovery of ATP levels after ischemia/reperfusion injury. We have, therefore, evaluated protein kinase C modulation of the F(1)F(0) ATPase in neonatal cardiac myocytes. Exposure of cells to 3 or 100 nM 4beta-phorbol 12-myristate-13-acetate induced co-immunoprecipitation of delta protein kinase C (but not alpha, epsilon, or zeta protein kinase C) with the d subunit of the F(1)F(0) ATPase. This co-immunoprecipitation correlated with 40+/-3% and 72+/-9% inhibitions of oligomycin-sensitive F(1)F(0) ATPase activity, respectively. We observed prominent expression of delta protein kinase C in cardiac myocyte mitochondria, which was enhanced following a 4-h hypoxia exposure. In contrast, hypoxia decreased mitochondrial zetaPKC levels by 85+/-1%. Following 4 h of hypoxia, F(1)F(0) ATPase activity was inhibited by 75+/-9% and delta protein kinase C co-immunoprecipitated with the d subunit of F(1)F(0) ATPase. In vitro incubation of protein kinase C with F(1)F(0) ATPase enhanced F(1)F(0) activity in the absence of protein kinase C activators and inhibited it in the presence of activators. Recombinant delta protein kinase C also inhibited F(1)F(0) ATPase activity. Protein kinase C overlay assays revealed delta protein kinase C binding to the d subunit of F(1)F(0) ATPase, which was modulated by diacylglycerol, phosphatidylserine, and cardiolipin. Our results suggest a novel regulation of the F(1)F(0) ATPase by the delta protein kinase C isozyme.

Decrease in oxidative phosphorylation yield in presence of butyrate in perfused liver isolated from fed rats

Background

Butyrate is the main nutrient for the colonocytes but the effect of the fraction reaching the liver is not totally known. A decrease in tissue ATP content and increase in respiration was previously demonstrated when livers were perfused with short-chain fatty acids (SCFA) such as butyrate, or octanoate.

In fed rats the oxidative phosphorylation yield was determined on the whole isolated liver perfused with butyrate in comparison with acetate and octoanoate (3 mmol/L). The rate of ATP synthesis was determined in the steady state by monitoring the rate of ATP loss after inhibition of (i) cytochrome oxidase (oxidative phosphorylation) with KCN (2.5 mmol/L) and (ii) glyceraldehyde 3-phosphate dehydrogenase (glycolysis) with IAA (0.5 mmol/L). The ATP flux, estimated by ³¹P Nuclear Magnetic Resonance, and the measured liver respiration allowed the ATP/O ratio to be determined.

Results

ATP turnover was significantly lower in the presence of butyrate (0.40 ± 0.10 μmoles/min.g, p = 0.001, n = 7) and octanoate (0.56 ± 0.10 μmoles/min.g, p = 0.01, n = 5) than in control (1.09 ± 0.13 μmoles/min.g, n = 7), whereas perfusion with acetate induced no significant decrease (0.76 ± 0.10 μmoles/min.g, n = 7). Mitochondrial oxygen consumption was unchanged in the presence of acetate (1.92 ± 0.16 vs 1.86 ± 0.16 for control) and significantly increased in the presence of butyrate (p = 0.02) and octanoate (p = 0.0004) (2.54 ± 0.18 and 3.04 ± 0.15 μmoles/min.g, respectively). The oxidative phosphorylation yield (ATP/O ratio) calculated in the whole liver was significantly lower with butyrate (0.07 ± 0.02, p = 0.0006) and octanoate (0.09 ± 0.02, p = 0.005) than in control (0.30 ± 0.05), whereas there was no significant change with acetate (0.20 ± 0.02).

Conclusion

Butyrate or octanoate decrease rather than increase the rate of ATP synthesis, resulting in a decrease in the apparent ATP/O ratio. Butyrate as a nutrient has the same effect as longer chain FA. An effect on the hepatic metabolism should be taken into account when large quantities of SCFA are directly used or obtained during therapeutic or nutritional strategies.

Alterations in oxidative phosphorylation complex proteins in the hearts of transgenic mice that overexpress the p38 MAP kinase activator, MAP kinase kinase 6

Ischemia-reperfusion (I/R) has critical consequences in the heart. Recent studies on the functions of I/R-activated kinases, such as p38 mitogen-activated protein kinase (MAPK), showed that I/R injury is reduced in the hearts of transgenic mice that overexpress the p38 MAPK activator MAPK kinase 6 (MKK6). This protection may be fostered by changes in the levels of many proteins not currently known to be regulated by p38. To examine this possibility, we employed the multidimensional protein identification technology MudPIT to characterize changes in levels of proteins in MKK6 transgenic mouse hearts, focusing on proteins in mitochondria, which play key roles in mediating I/R injury in the heart. Of the 386 mitochondrial proteins identified, the levels of 58 were decreased, while only 2 were increased in the MKK6 transgenic mouse hearts. Among those that were decreased were 21 mitochondrial oxidative phosphorylation complex proteins, which was unexpected because p38 is not known to mediate such decreases. Immunoblotting verified that proteins in each of the five oxidative phosphorylation complexes were reduced in MKK6 mouse hearts. On assessing functional consequences of these reductions, we found that MKK6 mouse heart mitochondria exhibited 50% lower oxidative respiration and I/R-mediated reactive oxygen species (ROS) generation, both of which are predicted consequences of decreased oxidative phosphorylation complex proteins. Thus the cardioprotection observed in MKK6 transgenic mouse hearts may be partly due to decreased electron transport, which is potentially beneficial, because damaging ROS are known to be generated by mitochondrial complexes I and III during reoxygenation.

Structure and expression of the atp operon coding for F1F0-ATP synthase from the antibiotic-producing actinomycete Nonomuraea sp. ATCC 39727

Nonomuraea sp. ATCC 39727 is a poorly characterized actinomycete, producer of the glycopeptide antibiotic A40926. In this study, the nucleotide sequence of the atp operon coding for F1F0-ATP synthase of Nonomuraea sp. ATCC 39727 was determined. It consisted of ten open reading frames arranged in the order atpI (encoding the i protein), orfX, atpB (a subunit), atpE (c subunit), atpF (b subunit), atpH (delta subunit), atpA (alpha subunit), atpG (gamma subunit), atpD (beta subunit) and atpC (epsilon subunit). The orfX coded for a putative small hydrophobic 71 amino acid peptide of unknown function related to several bacterial permeases. Its presence appeared to be a distinctive feature of the atp operon of phylogenetically distant actinobacteria. Transcription of the atp operon was evaluated. The results of northern blot and RT-PCR experiments demonstrated that the atp genes were co-transcribed into a single polycistronic mRNA. Real-time RT-PCR data provided evidence showing that transcription of the atp operon was biphasic during Nonomuraea growth. The amount of the atpD transcript decreased at the end of the exponential growth phase, and then moderately increased during the early stationary phase when, in contrast, the levels of ctaC, encoding the cytochrome c oxidase subunit II, progressively decreased. Western blot analysis confirmed that ATP synthase was also present in the membrane during the stationary phase. These results together with previous data demonstrate that oligomycin-sensitive ATP-driven proton pumping activity remained constant in the stationary phase; in contrast, the activity and cytochrome content of the respiratory enzymes became negligible.

Oxidative modification of mitochondrial respiratory complexes in response to the stress of Trypanosoma cruzi infection

Previously, we have shown deficiencies in the activities of the mitochondrial respiratory complexes and reduced mitochondrial ATP generation capacity in chagasic hearts infected by Trypanosoma cruzi. In this study, we determined whether the oxidative stress that occurs in response to T. cruzi infection contributes to the catalytic impairment of respiratory complexes and to subsequent mitochondrial dysfunction in murine myocardium. Our data show that oxidative injuries, as determined by the levels of lipid peroxides and protein carbonyls, are incurred in cardiac mitochondria as early as 3 days postinfection and persist throughout the infection and disease. The individual components of the respiratory complexes were separated by two-dimensional, blue-native gel electrophoresis, and carbonyl adducts were detected by Western blotting. We observed substantial carbonylation of the specific subunits of mitochondrial respiratory complexes in infected murine hearts. Of note is the oxidative modification of NDUFS1, NDUFS2, and NDUFV1, which form the catalytic core of the CI complex; UQCRC1, UQCRC2, and UQCRQ, the subunits of the core subcomplex, and UQCRH and CYC1, which form the cyt c(1) subcomplex of CIII; and a gamma chain that is essential for ATP synthesis by CV complex. The extent of oxidative modifications of the subunits correlated with the catalytic defects of the respiratory complexes in the infected myocardium. Taken together, our data demonstrate that respiratory complexes are oxidatively damaged in response to the stress of T. cruzi infection. These data also suggest involvement of the specific susceptibility of the protein subunits, and not generalized mitochondrial oxidative damage in respiratory chain impairment of chagasic hearts.

Structure-function relationship in P-type ATPases--a biophysical approach

P-type ATPases are a large family of membrane proteins that perform active ion transport across biological membranes. In these proteins the energy-providing ATP hydrolysis is coupled to ion-transport that builds up or maintains the electrochemical potential gradients of one or two ion species across the membrane. P-type ATPases are found in virtually all eukaryotic cells and also in bacteria, and they are transporters of a broad variety of ions. So far, a crystal structure with atomic resolution is available only for one species, the SR Ca-ATPase. However, biochemical and biophysical studies provide an abundance of details on the function of this class of ion pumps. The aim of this review is to summarize the results of preferentially biophysical investigations of the three best-studied ion pumps, the Na,K-ATPase, the gastric H,K-ATPase, and the SR Ca-ATPase, and to compare functional properties to recent structural insights with the aim of contributing to the understanding of their structure-function relationship.