In a model proposed for the structure of the .alpha.-subunit of the Escherichia coli f0f1-ATPase (Howitt, S.M., Gibson, f. and Cox, G.B. (1988) Biochim. Biophys. Acta 936, 74-80), a cluster of charged residues, includ...
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In a model proposed for the structure of the .alpha.-subunit of the Escherichia coli f0f1-ATPase (Howitt, S.M., Gibson, f. and Cox, G.B. (1988) Biochim. Biophys. Acta 936, 74-80), a cluster of charged residues, including one arginine and four aspartic acid residues, lie on the periplasmic side of the membrane. On the cytoplasmic side, three pairs of lysine residues and an arginine residue are present. Site-directed mutagenesis was used to investigate the roles of these residues. It was found that none was directly involved in the proton pore. However, the substitutions of Asp-124 or Asp-44 by asparagine or Arg-140 by glutamine had similar effects in that the membranes from such mutants from which the f1-ATPase was removed were proton-impermeable. A combination of the Asp-44 mutation with either the Asp-124 or Arg-140 mutations in the same strain resulted in complete loss of oxidative phosphorylation. It was tentatively concluded that Asp-124 and Arg-140 form a salt bridge, as did Asp-44 with an unknown residue, and these salt bridges were concerned with the maintenance of correct .alpha.-subunit structure. further support for this conclusion was obtained when second site revertants of a Glu-219 to histidine mutant were found to have either histidine or leucine replacing Arg-140. Thus, the lack of the Asp-124/Arg-140 salt bridge might enable repositioning of the helics of the .alpha.-subunit such that His-219 becomes a functional component of the proton pore.
The conditions for a competitive binding radioimmunoassay of rat α 1 -fetoprotein, sensitive and reproducible at the nanogram level, are described. Careful selection of the antiserum dilution and incubation times per...
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The conditions for a competitive binding radioimmunoassay of rat α 1 -fetoprotein, sensitive and reproducible at the nanogram level, are described. Careful selection of the antiserum dilution and incubation times permits approximately a 10-fold increase in the sensitivity of the radioimmunoassay. The mean serum α 1 f concentration for normal adult male Buffalo rats is 0·026 ± 0·0012 (SEM) μ g/ml.
Survey-based abundance indices (catch per unit effort, cpue) and harvest ratios (HRs) are usable proxies for spawning-stock biomass and fishing mortality (f). Here, we present an easy approach to calculate secondary i...
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Survey-based abundance indices (catch per unit effort, cpue) and harvest ratios (HRs) are usable proxies for spawning-stock biomass and fishing mortality (f). Here, we present an easy approach to calculate secondary indicators based on a public dataset. However, the performance of different cpue/HR indicator metrics varied between stocks, and, therefore, the adequate metrics for secondary indicators should be chosen for each stock after careful analysis by experts.
Redox titration off1-ATPase from rat liver mitochondria referred to the modification of the hydrolytic activity on Mg-ATP has resulted in a three-step pattern, with three distinct jumps of activity separated by clear...
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Redox titration off1-ATPase from rat liver mitochondria referred to the modification of the hydrolytic activity on Mg-ATP has resulted in a three-step pattern, with three distinct jumps of activity separated by clear plateaus. The measured potentials ranged from -400 mV to +400 mV and were obtained by the addition of dithionite and ferricyanide. Electron exchange was facilitated with a mixture of different redox mediators. At pH 7.4 the midpoint potentials were +210 mV, +40 mV and -230 mV. These three midpoint potentials were displaced towards more negative values by 2,4-dinitrophenol or by an increase of the pH of the medium. The titration curves were described by n = 2 Nernst equations.
Binding of about 1 mol of adenosine triphosphopyridoxal to Escherichia coli f1-ATPase resulted in the nearly complete inactivation of the enzyme [(1987) J. Biol. Chem. 262, 7686-7692]. About two thirds of the label wa...
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Binding of about 1 mol of adenosine triphosphopyridoxal to Escherichia coli f1-ATPase resulted in the nearly complete inactivation of the enzyme [(1987) J. Biol. Chem. 262, 7686-7692]. About two thirds of the label was bound to the alpha-subunit, and the rest to the beta-subunit. The present study revealed that Lys201 in the alpha-subunit and Lys155 in the glycine-rich region of the beta-subunit are the major sites labeled with this reagent. Thus, these two residues might be located close to the gamma-phosphate of the bound ATP.
The rate of inactivation off 1 -ATPase, isolated from beef heart mitochondria, by the active acidic form of the natural inhibitor protein depends on the ATP concentration. An increase in concentration of ATP to ∼ 20...
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The rate of inactivation off 1 -ATPase, isolated from beef heart mitochondria, by the active acidic form of the natural inhibitor protein depends on the ATP concentration. An increase in concentration of ATP to ∼ 20 μM leads to a decrease in that of the inhibitor protein inducing 50% inhibition of the f 1 -ATPase during 5 s preincubation ( C 50 ); further increase in ATP concentration to 1 mM causes little, if any, change in C 50 . However, the C 50 values show a rise at ATP concentrations higher than 1 mM. This ATP dependence of the inhibitor action may be in agreement with a version of the alternating-site binding-change mechanism, which assumes that the two-site catalytic cycle intermediates possessing (i) the products (ADP + P i ) bound in the low-affinity state at one of the active sites and (ii) an ATP molecule at the other active site are the targets for the acidic form of the inhibitor protein.
This study compares the test results of the fAST (fabric Assurance by Simple Testing) with those of the KES - f (Kawabata Evaluation Systems for fabrics) for a range of nineteen light weight wool and wool blend fabric...
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This study compares the test results of the fAST (fabric Assurance by Simple Testing) with those of the KES - f (Kawabata Evaluation Systems for fabrics) for a range of nineteen light weight wool and wool blend fabrics in terms of the low - stress mechanical properties of bending, shear, and tensile deformation. It is found that there are very significant correlations between the corresponding parameters for extensibility and shear rigidity obtained from the test results of the two systems. The correlation between the values of bending rigidity obtained from the two systems is only moderate. furthermore, for the fabrics tested in this study, the values of bending rigidity, shear rigidity, and extensibility measured using the KES - f instruments are higher than those of the corresponding parameters measured using the fAST instruments. The linear regression equation is given for each pair of corresponding parameter.
Transport of cytoplasmically synthesized precursor proteins into or across the inner mitochondrial membrane requires a mitochondrial membrane potential. We have studied whether additional energy sources are also neces...
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Transport of cytoplasmically synthesized precursor proteins into or across the inner mitochondrial membrane requires a mitochondrial membrane potential. We have studied whether additional energy sources are also necessary for protein translocation. Reticulocyte lysate (containing radiolabelled precursor proteins) and mitochondria were depleted of ATP by pre-incubation with apyrase. A membrane potential was then established by the addition of substrates of the electron transport chain. Oligomycin was included to prevent dissipation of delta psi by the action of the f0f1-ATPase. Under these conditions, import of subunit beta off1-ATPase (f1 beta) was inhibited. Addition of ATP or GTP restored import. When the membrane potential was destroyed, however, the import off1 beta was completely inhibited even in the presence of ATP. We therefore conclude that the import off1 beta depends on both nucleoside triphosphates and a membrane potential.
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