Microtubule-associated protein 2c reorganizes both microtubules and microfilaments into distinct cytological structures in an actin-binding protein-280-deficient melanoma cell line

The emergence of processes from cells often involves interactions between microtubules and microfilaments. Interactions between these two cytoskeletal systems are particularly apparent in neuronal growth cones. The juvenile isoform of the neuronal microtubule-associated protein 2 (MAP2c) is present in growth cones, where we hypothesize it mediates interactions between microfilaments and microtubules. To approach this problem in vivo, we used the human melanoma cell, M2, which lacks actin-binding protein-280 (ABP-280) and forms membrane blebs, which are not seen in wild-type or ABP-transfected cells. The microinjection of tau or mature MAP2 rescued the blebbing phenotype; MAP2c not only caused cessation of blebbing but also induced the formation of two distinct cellular structures. These were actin-rich lamellae, which often included membrane ruffles, and microtubule-bearing processes. The lamellae collapsed after treatment with cytochalasin D, and the processes retracted after treatment with colchicine. MAP2c was immunocytochemically visualized in zones of the cell that were devoid of tubulin, such as regions within the lamellae and in association with membrane ruffles. In vitro rheometry confirmed that MAP2c is an efficient actin gelation protein capable of organizing actin filaments into an isotropic array at very low concentrations; tau and mature MAP2 do not share this rheologic property. These results suggest that MAP2c engages in functionally specific interactions not only with microtubules but also with microfilaments.

Identification of the region in actin-binding protein that binds to the cytoplasmic domain of glycoprotein IBalpha

Actin-binding protein (ABP-280) is a component of the submembranous cytoskeleton and interacts with the glycoprotein (GP) Ibalpha subunit of the GP Ib-IX complex in platelets. In the present studies, we have identified the binding site for GP Ibalpha in ABP-280. A melanoma cell line lacking ABP-280 was stably transfected with the cDNAs coding for GP Ib-IX, then transiently transfected with cDNA coding for various carboxyl-truncates of ABP-280. Immunocapture assays and co-immunoprecipitation experiments from detergent-lysed cells showed that deletion of the carboxyl-terminal repeats 20-24 of ABP-280 had no effect on GP Ib-IX binding, but deletion of residues 2099 through 2136 within repeat 19 abolished binding. In the yeast two-hybrid system, an ABP-280 fragment comprising repeats 17-19 bound GP Ibalpha. Deletion from either end abolished binding. Individual or multiple repeats of ABP-280 were expressed as fusion protein in bacteria and purified; structural folding was evaluated, and binding to GP Ib-IX was assessed. Binding depended on the presence of repeats 17-19. None of the individual repeats were able to bind to GP Ib-IX. These findings demonstrate that residues 1850-2136 comprising repeats 17-19 contain the binding site for GP Ib-IX.

Differential effects of chronic ethanol consumption on hepatic mitochondrial and cytoplasmic ribosomes

The effects of chronic ethanol consumption on the properties of mitochondrial and cytoplasmic ribosomes were investigated in rat liver. Sedimentation properties of purified mitochondrial (55S) and cytoplasmic (80S) ribosomes were determined by analyses on sucrose density gradients. Mitochondrial ribosomes from control animals moved further in the gradients than did those isolated from ethanol-fed rats, which suggests that ethanol ribosomes have a lower molecular weight. In addition, mitochondrial from ethanol-fed animals contained a lower percentage of ribosomes present as the intact monosome, suggesting that ethanol may have an effect on the stability of the functional mitochondrial ribosomes. This was confirmed by the presence of the larger 39S subunit in preparations from ethanol-fed animals. No such ethanol-related alterations were seen with cytoplasmic ribosomes. The protein composition of mitochondrial cytoplasmic ribosomes was investigated using two-dimensional gel electrophoresis, followed by two-dimensional densitometry. As indicated by differences in protein staining intensity, ethanol consumption seemed to alter the concentration of seven mitochondrial ribosomal proteins. In contrast, no such changes were observed in the protein pattern from cytoplasmic ribosomes. Observations in this study provide for the possibility that alterations in the amounts of selected proteins in the mitochondrial ribosome lead to impaired assembly of the ribosome. These ethanol-related structural changes may be responsible for the decreased activity of mitochondrial ribosomes that results in impaired hepatic mitochondrial protein synthesis (W.B. Coleman and C.C. Cunningham, Biochim. Biophys, Acta 1058:178-186, 1991). Furthermore, this study reemphasizes the increased susceptibility of the hepatic mitochondrial translation system, compared with the cytoplasmic system to chronic ethanol consumption.

Renal epithelial protein (Apx) is an actin cytoskeleton-regulated Na+ channel

Apx, the amphibian protein associated with renal amiloride-sensitive Na+ channel activity and with properties consistent with the pore-forming 150-kDa subunit of an epithelial Na+ channel complex initially purified by Benos et al. (Benos, D. J., Saccomani, G., and Sariban-Sohraby, S.(1987) J. Biol. Chem. 262, 10613-10618), has previously failed to generate amiloride-sensitive Na+ currents (Staub, O., Verrey, F., Kleyman, T. R., Benos, D. J., Rossier, B. C., and Kraehenbuhl, J.-P.(1992) J. Cell Biol. 119, 1497-1506). Renal epithelial Na+ channel activity is tonically inhibited by endogenous actin filaments (Cantiello, H. F., Stow, J., Prat, A. G., and Ausiello, D. A.(1991) Am. J. Physiol. 261, C882-C888). Thus, Apx was expressed and its function examined in human melanoma cells with a defective actin-based cytoskeleton. Apx-transfection was associated with a 60-900% increase in amiloride-sensitive (Ki = 3 microM) Na+ currents. Single channel Na+ currents had a similar functional fingerprint to the vasopressin-sensitive, and actin-regulated epithelial Na+ channel of A6 cells, including a 6-7 pS single channel conductance and a perm-selectivity of Na+:K+ of 4:1. Na+ channel activity was either spontaneous, or induced by addition of actin or protein kinase A plus ATP to the bathing solution of excised inside-out patches. Therefore, Apx may be responsible for the ionic conductance involved in the vasopressin-activated Na+ reabsorption in the amphibian kidney.

Isolation and characterization of rat liver mitochondrial ribosomes

A procedure has been developed that allows characterization of mitochondrial ribosomes and quantitative analysis of the relative composition of constitutive ribosomal proteins. Purified mitochondrial ribosomes were isolated from two rat livers and shown to be active in catalyzing the polymerization of phenylalanine. They differ in sedimentation and spectral properties from cytoplasmic ribosomes isolated from the same livers. The number and relative composition of proteins present in active rat liver mitochondrial ribosomes were investigated using two-dimensional nonequilibrium pH gradient electrophoresis. There were 86 proteins found associated with mitochondrial ribosomes in contrast to 70 proteins found associated with cytoplasmic ribosomes. Comparison of electrophoretic patterns revealed that cytoplasmic ribosomal proteins were considerably more basic than their mitochondrial counterparts. Densitometry demonstrated that the relative changes in the concentrations of these proteins can be measured quantitatively. These procedures, developed for use with two rat livers, allow the rat to be used as an efficient model for further studies into disease states of mitochondrial translation.

Effect of chronic ethanol consumption on the energy state and structural stability of periportal and perivenous hepatocytes

This study was implemented to evaluate whether perivenous cells experience functional alterations due to a deficit in oxygen tension resulting from ethanol oxidation in the periportal regions of the lobule. Periportal and perivenous hepatocytes were prepared from ethanol-fed and control animals (Lieber-DeCarli diet, 31 days). These cells were either incubated at various oxygen tensions by varying the composition of the gases utilized to equilibrate the incubation buffers (0, 5, 25, and 95% oxygen) or they were unincubated. They were analyzed for adenine nucleotide and inorganic phosphate concentrations and from these data phosphorylation potentials and energy charge values were determined. Under highly aerobic conditions no differences were observed in the energy states of the cells irrespective of their source (control vs ethanol-fed; periportal vs perivenous). The ATP concentrations, phosphorylation potentials, and energy charge values indicated that the energy states of cells from both ethanol-fed and control rats were maintained at relatively high levels in incubations with 5 and 25% oxygen. However, unincubated cells and those incubated at 0% oxygen demonstrated lowered energy states and the decreases were most striking in hepatocytes from ethanol-fed animals. Measurements of LDH loss and trypan blue exclusion indicate that cell leakage and viability loss occur when cells are incubated under anoxic and hypoxic conditions. At low oxygen tensions perivenous cells from ethanol-fed rats demonstrated much greater loss of structural stability than did the other cell preparations. These observations indicate that decreased energy state is one factor which contributes to cell damage in hepatocytes from ethanol-fed animals. Moreover, perivenous cells from ethanol-fed animals seem to be particularly vulnerable to damage under hypoxic conditions.

Actin polymerization and intracellular solvent flow in cell surface blebbing

The cortical actin gel of eukaryotic cells is postulated to control cell surface activity. One type of protrusion that may offer clues to this regulation are the spherical aneurysms of the surface membrane known as blebs. Blebs occur normally in cells during spreading and alternate with other protrusions, such as ruffles, suggesting similar protrusive machinery is involved. We recently reported that human melanoma cell lines deficient in the actin filament cross-linking protein, ABP-280, show prolonged blebbing, thus allowing close study of blebs and their dynamics. Blebs expand at different rates of volume increase that directly predict the final size achieved by each bleb. These rates decrease as the F-actin concentration of the cells increase over time after plating on a surface, but do so at lower concentrations in ABP-280 expressing cells. Fluorescently labeled actin and phalloidin injections of blebbing cells indicate that a polymerized actin structure is not present initially, but appears later and is responsible for stopping further bleb expansion. Therefore, it is postulated that blebs occur when the fluid-driven expansion of the cell membrane is sufficiently rapid to initially outpace the local rate of actin polymerization. In this model, the rate of intracellular solvent flow driving this expansion decreases as cortical gelation is achieved, whether by factors such as ABP-280, or by concentrated actin polymers alone, thereby leading to decreased size and occurrence of blebs. Since the forces driving bleb extension would always be present in a cell, this process may influence other cell protrusions as well.

Differential effects of ethanol consumption on synthesis of cytoplasmic and mitochondrial encoded subunits of the ATP synthase

The relative concentrations of several subunits of the mitochondrial F0.F1-ATP synthase were determined in mitochondria and submitochondrial particles prepared from the livers of ethanol-fed and control rats. The polypeptides were separated by sodium dodecylsulfate-polyacrylamide gel electrophoresis and the stained gels were analyzed by densitometry for the relative concentrations of the ATP synthase subunits. A significant decrease in the relative concentration of the mitochondrial gene product, ATPase subunit 8, was observed in mitochondria and submitochondrial particles from ethanol-fed animals. The relative concentration of the other mitochondrial encoded ATPase subunit, ATPase 6, was also depressed, as confirmed in submitochondrial particles. In contrast, there were no significant ethanol-related depressions in subunits alpha, beta, and OSCP of the F0.F1 or the adenine nucleotide carrier in intact mitochondria. These results demonstrate that ethanol consumption causes a decrease in the content of mitochondrial synthesized subunits 6 and 8 whereas no effect is exerted on the concentrations of nuclear gene products of the ATP synthase complex. Likewise, the adenine nucleotide transporter, also a nuclear gene product, is unaffected by ethanol consumption.

Alcoholism and myocardial energy metabolism

A review of the effects of chronic ethanol consumption on myocardial energy metabolism in animal models reveals that alterations in cardiac function are not accompanied by changes in the levels of the high-energy metabolites, ATP, and creatine phosphate. There are minor alterations in mitochondrial ultrastructure and function that appear to be accentuated by lowered nutrient intake. Observations to date indicate that, in animal models, there is an interaction between chronic ethanol consumption and caloric deprivation in eliciting alterations in myocardial energy metabolism. Furthermore, ethanol-related ultrastructural changes and depressed mitochondrial function are much more demonstrable in liver than in heart, suggesting strongly that the myocardium is less susceptible to the deleterious effects of alcohol than is the liver.

A human lymphocytotoxic autoantibody is encoded by antibody variable region genes in their germ line configuration

Lymphocytotoxic autoantibodies are commonly found in sera from kidney dialysis patients, where they interfere with interpretation of the crossmatch test. We have produced a monoclonal lymphocytotoxic autoantibody by EBV transformation of PBLs from a dialysis patient, followed by fusion of the transformed cells with a heteromyeloma. The autoantibody derived, called FWE, was IgM kappa class and its pattern of reactivity against T and B lymphocytes, cells from patients with chronic lymphocytic leukemia and K562, was similar to that described for lymphocytotoxic autoantibodies found in sera. It was absorbed by fetal but not adult human erythrocytes, suggesting the antigenic determinant might be the blood group antigen i. cDNA encoding the variable domain of FWE was amplified by polymerase chain reaction, cloned into the vector M13 mp18, and sequenced. The variable region of the kappa light chain (V kappa) was 98.8% identical over a 260-bp stretch with a known germ line sequence and the junctional (J kappa) region was identical over 16 bp with the germ line sequence J kappa 2. The variable region of the heavy chain (VH) was 99.3% identical over a 268-bp overlap with the germ line gene VH4.21, a member of the VHIV family, and the junctional region of the heavy chain (JH) was identical with the germ line JH gene JH5 over 46 bp, with a truncated 5' end. The diversity region was not identified. These data suggest that the genes required to produce human lymphocytotoxic autoantibodies are encoded within the germ line and, therefore, that all dialysis patients may be able to produce them under certain circumstances.

Actin-binding protein contributes to cell volume regulatory ion channel activation in melanoma cells

The cell volume regulatory response to a hypotonic stimulus is frequently initiated by activation of K+ and Cl- channels. We have characterized the hypotonic cell volume regulatory response of human melanoma cells devoid of actin-binding protein (ABP) and their genetically rescued counterpart transfected with the cDNA for ABP. ABP-deficient cells were unable to volume-regulate or activate K+ channels when exposed to a hypotonic stimulus. Genetic rescue with ABP resulted in recovery of both the cell volume regulatory response and the osmotically linked K+ channel activation. These data are consistent with a functional interaction between the actin cytoskeleton and osmotically sensitive ion transport.

The use of the Ways of Coping (Revised) questionnaire with parents of children with Down's syndrome

The principal aim of this study was to assess the validity and usefulness of the Ways of Coping (Revised) questionnaire (Folkman & Lazarus, 1985) with a British sample of parents of children with Down's syndrome. Factor analysis yielded five subscales which were compared with those reported elsewhere. Other properties of the instrument were investigated. It was concluded that the instrument was potentially valuable to those investigating coping in families with special problems.

Actin structural proteins in cell motility

The machinery for cell locomotion is based in a network of polymerized actin filaments supporting the peripheral cytoplasm. This network or 'gel' consists of actin filaments in a variety of configurations, including cables, loose bundles, and branching arrays; all formed by the interaction of actin-associated proteins with actin filaments. For cell locomotion to occur, this network must be reversibly disassembled or 'solated' to allow protrusion, then re-assembled to stabilize the resulting extension. Thus, proteins to promote both 'solation' and 'gelation' of actin are important for efficient cell locomotion. Because of their distribution, control, and in vitro effects on actin filaments, two such proteins, gelsolin and actin-binding protein (ABP) should play especially important roles in cell motility. Support for this premise is found in in vivo studies of mouse kidney fibroblasts which demonstrated increased translocational locomotion after cytoplasmic gelsolin expression was increased genetically and in melanoma cells missing actin-binding protein which behave as expected for a cell unable to achieve efficient actin gelation. Since malignant transformation is known to affect the expression and distribution of several of these actin structural proteins, including gelsolin, further investigations of the role these proteins play in cell motility will be important to the determination of tumor cell motility and hence metastatic propensity.

Actin-binding protein requirement for cortical stability and efficient locomotion

Three unrelated tumor cell lines derived from human malignant melanomas lack actin-binding protein (ABP), which cross-links actin filaments in vitro and connects these filaments to plasma membrane glycoproteins. The ABP-deficient cells have impaired locomotion and display circumferential blebbing of the plasma membrane. Expression of ABP in one of the lines after transfection restored translocational motility and reduced membrane blebbing. These findings establish that ABP functions to stabilize cortical actin in vivo and is required for efficient cell locomotion.

Effect of chronic ethanol consumption on hepatic mitochondrial transcription and translation

Liver mitochondria from ethanol-fed rats display an impaired ability for protein synthesis in vitro. Studies were conducted to explore the possible mechanisms which might account for this impaired capacity of ethanol mitochondria for protein synthesis. The present studies did not demonstrate any significant ethanol-induced lesion in mitochondrial nucleic acid metabolism in organelles isolated from ethanol-fed rats for any of the parameters investigated (mtDNA content, steady-state mtRNA concentration, mtRNA polymerase activity, concentration of specific mRNAs and rRNAs, mtRNA processing). An investigation of ribosome function in isolated mitochondria demonstrated significant decreases in the number of active ribosomes (55% fewer) in mitochondria from ethanol-fed rats. Initiation of protein synthesis was also significantly depressed (46%) in ethanol mitochondria. In addition, the yield of ribosomal particles from ethanol mitochondria was decreased 32% as compared to the yield of ribosomal particles from control mitochondria. However, isolated ribosomes from ethanol mitochondria were determined to be fully functional in a poly(U)-directed phenylalanine polymerization system. Soluble translation factors from ethanol mitochondria were also found to support full activity of control ribosomes in a poly(U)-directed phenylalanine polymerization system. These results suggest strongly that the ethanol-induced depression of mitochondrial protein synthesis is due to a decrease in the number of competent ribosomes in hepatic mitochondria from chronically ethanol-fed rats.

Enhanced motility in NIH 3T3 fibroblasts that overexpress gelsolin

Increasing the content of the actin-binding protein gelsolin in cultured mouse fibroblasts by up to 125 percent by gene transfection proportionally enhanced the rate at which the cells migrated through porous filters toward a gradient of serum and closed a wound made on a confluent monolayer of cells in a tissue culture dish. These results provide direct evidence that gelsolin, which promotes both actin assembly and disassembly in vitro, is an important element in fibroblast locomotion and demonstrate that the manipulation of intracellular machinery can increase cell motility.

Tightly associated cardiolipin in the bovine heart mitochondrial ATP synthase as analyzed by 31P nuclear magnetic resonance spectroscopy

The bovine heart F0F1-ATPase preparation (Serrano, R., Kanner, B., and Racker, E. (1976) J. Biol. Chem. 251, 2453-2461) has been further delipidated. The lipid-deficient preparation contained 2.5 mol of cardiolipin, 1 mol of phosphatidylcholine (PC), and 1 mol of phosphatidylethanolamine (PE) per mol of F0F1. When reconstituted with asolectin the delipidated preparation exhibited an activity of 13 mumol of ATP hydrolyzed/min/mg of protein which was 88% oligomycin-sensitive. The phospholipids in this preparation were analyzed by 31P NMR spectroscopy to determine if they were immobilized by the enzyme (rendered NMR-invisible). The PC and PE were below the limits of detection under the conditions utilized and the cardiolipin was NMR-invisible until the enzyme was denatured by addition of either 1% sodium dodecyl sulfate or 8 M urea. Addition of cardiolipin to the delipidated preparation and subsequent analysis by NMR spectroscopy revealed that approximately 4 mol of cardiolipin were immobilized per mol of F0F1 ATPase. The enzyme appears to have high affinity for cardiolipin exclusively, since PC (a prominent inner membrane lipid), phosphatidyl serine (an acidic phospholipid), and phosphatidyl glycerol (the precursor to cardiolipin) were not immobilized (rendered NMR-invisible) when added to the delipidated preparation.

Effects of chronic ethanol consumption on the synthesis of polypeptides encoded by the hepatic mitochondrial genome

Liver mitochondria from rats fed ethanol chronically demonstrate an impaired ability to incorporate [35S]methionine into polypeptide products in vitro. This ethanol-induced effect on mitochondrial translation in vitro could not be attributed to significant differences in the methionine precursor pool sizes of ethanol and control mitochondria or to the acute effects of residual ethanol. The observed reduction of radiolabeled methionine incorporation into mitochondrial gene products of ethanol mitochondria in vitro reflects a decrease in the synthesis of all the mitochondrial gene products. However, the percentage of total radiolabel incorporated into each gene product is unaffected by ethanol, suggesting an ethanol-induced coordinate depression of mitochondrial protein synthesis. Moreover, SDS-PAGE and densitometry of submitochondrial particles from ethanol-fed and control rats demonstrated that the steady-state concentration of each of the mitochondrial gene products is decreased in ethanol-fed rats. This reduction of the steady-state concentration of the mitochondrial gene products may be related to the observed depressions of oxidative phosphorylation activities associated with hepatic mitochondria from ethanol-fed rats.

The effects of chronic ethanol consumption on hepatic mitochondrial energy metabolism

Chronic ethanol consumption results in a generalized depression in hepatic mitochondrial energy metabolism. Both the rate and efficiency of ATP synthesis via the oxidative phosphorylation system are decreased. Alterations in the activities of several components of the oxidative phosphorylation system contribute to the overall decrease in the capacity for ATP synthesis. There appears to be no alteration in any particular component which is rate-limiting. Although changes in membrane lipids may play a minor role, it appears that the decreased levels of mitochondria-derived polypeptide components of the oxidative phosphorylation system are primarily responsible for the depression in both the rate and efficiency of ATP synthesis. The concentrations of these mitochondrial gene products are lowered due to effects of chronic ethanol consumption on the mitochondrial translational process.

Comparison of effects of long-term ethanol consumption on the heart and liver of the rat

Alterations in heart and liver metabolism were determined periodically in Sprague-Dawley rats pair-fed a liquid diet (ethanol, 36% of calories) for times as long as 1 year. In liver mitochondria the rate of ATP synthesis was lowered significantly after ethanol administration for 1 month and longer feeding periods. In liver microsomes from ethanol-fed animals, ethanol oxidation and aniline hydroxylation increased 1.5- and 3.5-fold, respectively, after 1 month and remained elevated at the longer feeding intervals. Electron microscopic analyses of heart left ventricles revealed no alterations from ethanol consumption for 1 month. Alterations including disrupted mitochondrial cristae, dilatation of sarcoplasmic reticulum, and widening of the intercalated discs were observed after 6.5-month feeding periods. Myocardial concentrations of creatine, creatine phosphate, ATP, ADP, and Pi remained constant even after ethanol consumption for 9 months. After a 12-month feeding period slight changes in cardiac mitochondrial energy-linked properties were observed which were not as pronounced as those occurring in liver mitochondria. The activity and oligomycin sensitivity of the ATPase were not altered in cardiac mitochondria, whereas in liver preparations significant alterations in these properties of the ATPase were apparent after ethanol consumption for 1 month and the longer feeding periods. These observations suggest that the liver responds more quickly and dramatically to chronic ethanol consumption than does the heart.

Apparent response of refractory post-transfusion purpura to splenectomy

Post transfusion purpura (PTP) is a rare disorder characterized by the abrupt onset of severe thrombocytopenia following transfusion. A patient with PTP and massive bleeding was refractory to corticosteroids, gamma globulin, and plasma exchange but developed an immediate and sustained rise in platelet count following splenectomy. Splenectomy may be a useful therapeutic modality in patients with refractory PTP.

Control of state 3 respiration in liver mitochondria from rats subjected to chronic ethanol consumption

Male Sprague-Dawley rats were pair-fed a liquid diet containing 36% of calories as ethanol for at least 31 days. Mitochondria were isolated from the livers and assayed for state 3, state 4 and uncoupled respiration at all three coupling sites. Assay conditions were established that maximized state 3 respiration with each substrate while maintaining a high respiratory control ratio. In mitochondria from ethanol-fed animals, state 3 respiratory rates were decreased at all three coupling sites. The decreased state 3 rate observed at site III was still significantly higher than the state 3 rates observed at site II in mitochondria from either ethanol-fed or control animals. Moreover, the maximal (FCCP-uncoupled) rates with succinate and alpha-ketoglutarate were the same in mitochondria from ethanol-fed and control animals, whereas with glutamate-malate as substrate it was lowered 23% by chronic ethanol consumption. To investigate the role of cytochrome oxidase in modulating the respiratory rate with site I and site II substrates, the effects of cyanide on state 3 and FCCP-uncoupled respiration were determined. When the mitochondria were uncoupled there was no decrease in the rate of succinate oxidation until the rates of ascorbate and succinate oxidation became equivalent. Conversely, parallel inhibition of ascorbate, succinate and glutamate-malate state 3 respiratory rates were observed at all concentrations (1-50 microM) of cyanide utilized. These observations suggest strongly that in coupled mitochondria ethanol-elicited decreases in cytochrome oxidase activity depress the state 3 respiratory rates with site I and II substrates.

Ethanol-elicited alterations in the oligomycin sensitivity and structural stability of the mitochondrial F0 . F1 ATPase

Liver mitochondria from rats fed ethanol chronically demonstrated a 35% decrease in mitochondrial ATPase activity. Moreover, the ATPase activity was inhibited only 61% by addition of oligomycin. Treatment of mitochondria from ethanol-fed rats with the detergent, Lubrol-WX, caused the release of 36% of the F1 from the resulting inner membrane particles. In comparison, only 5% of the F1 was dissociated when control mitochondria were subjected to the Lubrol treatment. However, when the units of ATPase activity from the supernatant and particles obtained after Lubrol treatment were added together, their sums were equivalent in preparations from control and ethanol-fed animals. Moreover, polyacrylamide gel electrophoresis analyses indicated equal amounts of the alpha + beta subunits of F1 in mitochondria from control and ethanol-fed rats. Reconstitution experiments with urea particles and F1 prepared from both control and ethanol mitochondria revealed a decrease in oligomycin sensitivity which could be attributed to an alteration in the functioning of either the oligomycin sensitivity conferring protein or a membrane sector subunit that interacts with oligomycin. Analysis by reconstitution also demonstrated that there were no ethanol-elicited alterations in the properties of the F1 portion of the ATP synthase complex. These observations indicate that the activity of the ATP synthase complex is altered significantly by ethanol-elicited changes in the functioning of those polypeptides involved in modulating both oligomycin sensitivity and the association of F1 with membrane sector subunits.