TITULO II LEY DE IMPUESTO A LOS INGRESOS Y UTILIDADES
ARTÍCULO 45.- Sobre el monto del incentivo
mem-brane. What is the formula that expresses the driving force in the concentration gradient,
22. Ballmoos, C. von, G. M. Cook, and P. Dimroth.
2008. Unique rotary ATP synthase and its biological diversity. Annu. Rev. Biophys. 37:43–64.
23. Cross, R. L. 1992. The reaction mechanism of F0F1-ATP synthases, pp. 317–330. In: Molecular Mechanisms in Bioenergetics. L. Ernster (Ed.).
Elsevier Science Publishers, Amsterdam.
24. Another way of stating this is in terms of the total force. The total force is equal to y∆p +∆Gp/F, where
∆Gp/F = 518 mV. At equilibrium the total force is 0;
therefore y∆p = –518 mV, and when y = 3, ∆p = –173 mV.
25. Kandpal, R. P., K. E. Stempel, and P. B. Boyer.
1987. Characteristics of the formation of enzyme-bound ATP from medium inorganic phosphate by mitochondrial F1 adenosine triphosphatase in the presence of dimethyl sulfoxide. Biochemistry 26:1512–1517.
26. Grubmeyer, C., R. L. Cross, and H. S. Penefsky.
1982. Mechanism of ATP hydrolysis by beef heart mitochondrial ATPase: rate constants for elemen-tary steps in catalysis at a single site. J. Biol. Chem.
257:12092–12100.
27. Vonck, J., T. K. von Nidda, T. Meier, U. Matthey, D. J. Mills, W. Kuhlbrandt, and P. Dimroth. 2002.
Molecular architecture of the undecameric rotor of a bacterial Na+-ATP synthase. J. Mol. Biol. 321:
307–316.
28. Kaim, G., M. Prummer, B. Sick, G. Zumofen, A.
Renn, U. P. Wild, and P. Dimroth. 2002. Coupled rotation within single F0F1 enzyme complexes dur-ing ATP synthesis or hydrolysis. FEBS Lett. 525:
156–163.
29. Capaldi, R. A., and R. Aggeler. 2002. Mechanism of the F1F0 ATP synthase, a biological rotary motor.
Trends Biochem. Sci. 27:154–160.
30. Fillingame, R. H., and O. Y. Dmitriev. 2002.
Structural model of the transmembrane F0 rotary sector of H+-transporting ATP synthase derived by solution NMR and intersubunit cross-linking in situ.
Biochim. Biophys. Acta 1565:232–245.
31. The ∆E0 can be a function of the pH. This is the case for the following reaction, where m is not zero: in some reactions n = 1 and m = 0 (cytochrome redox reactions), n = 2 and m = 1 (NAD+ or NADP+ redox reactions), n = 2 and m = 2 (fumarate–succi-nate redox reactions).
In reactions involving protons, if the pH is not zero, then the ∆E0 is more negative. When m = n, the
∆E0 is –60 mV/pH. When m = 1 and n = 2, the ∆E0 is –30 mV/pH. For more discussion of this subject, see ref. 2.
32. Reviewed in Unemoto, T., H. Tokuda, and M.
Hayashi. 1990. Primary sodium pumps and their signfi cance in bacterial energetics, pp. 33–54. In: T.
A. Krulwich (Ed.). The Bacteria, Vol. XII. Academic Press, New York.
10. Cecchini, G., and A. L. Koch. 1975. Effect of uncouplers on “downhill” β-galactoside transport in energy-depleted cells of Escherichia coli. J. Bacteriol.
123:187–195.
11. Gould, J. M., and W. A. Cramer. 1977.
Relationship between oxygen-induced proton effl ux and membrane energization in cells of Escherichia coli. J. Biol. Chem. 252:5875–5882.
12. E. Padan, D. Zilberstein, and S. Schuldiner.
1981. pH homeostasis in bacteria. Biochim. Biophys.
Acta 650:151–166.
13. Reviewed in: Cobley, J. G., and J. C. Cox.
1983. Energy conservation in acidophilic bacteria.
Microbiol. Rev. 47:579–595.
14. The pumping of protons out of the cell or the electrogenic infl ux of electrons will create a mem-brane potential, positive outside. However, in the aerobic acidophilic bacteria [i.e., bacteria that live in environments of extremely low pH (pH 1–4)], other events act to reverse the membrane potential.
These bacteria have positive membrane potentials (i.e., inside positive with respect to outside, at low pH). It is not clear why the aerobic acidophiles have a positive ∆Ψ. One possibility is that they have an energy-dependent K+ pump that brings K+ into the cells at a rate suffi cient to establish a net infl ux of positive charge, creating an inside positive mem-brane potential. This point is discussed further in Section 17.1.3.
15. Krulwich, T. A., and A. A. Guffanti. 1986.
Regulation of internal pH in acidophilic and alka-lophilic bacteria, pp. 352–365. In: Methods in Enzymology, Vol. 125. S. Fleischer and B. Fleischer (Eds.). Academic Press, New York.
16. Actually, what happens in the presence of nigeri-cin is that an equalization of the K+ and H+ gradients occurs.
17. Padan, E., D. Zilberstein, and S. Schuldiner.
1981. pH homeostasis in bacteria. Biochim. Biophys.
Acta 650:151–166.
18. Rottenberg, H. 1979. The measurement of membrane potential and ∆pH in cells, organelles, and vesicles. Methods Enzymol. 55:547–569.
19. Bakker, E. P. 1990. The role of alkali–cation transport in energy coupling of neutrophilic and aci-dophilic bacteria: an assessment of methods and con-cepts. FEMS Microbiol. Rev. 75:319–334.
20. This is because the resonance frequency of inor-ganic phosphate or of the γ-phosphate of ATP in a high magnetic fi eld is a function of the degree to which the phosphate is protonated. (See: Ferguson, S.
J., and M. C. Sorgato. 1982. Proton electrochemical gradients and energy-transduction processes. Annu.
Rev. Biochem. 51:185–217.)
21. Nicholls, D. G., and S. J. Ferguson. 2002.
Bioenergetics 3, pp. 195–217. Elsevier Science Ltd., London.
41. Dimroth, P. 1980. A new sodium-transport sys-tem energized by the decarboxylation of oxaloac-etate. FEBS Lett. 122:234–236.
42. Dimroth, P., and A. Thomer. 1988. Dissociation of the sodium-ion-translocating oxaloacetate decar-boxylase of Klebsiella pneumoniae and reconstitu-tion of the active complex from the isolated subunits.
Eur. J. Biochem. 175:175–180.
43. Hilpert, W., and P. Dimroth. 1983. Purifi cation and characterization of a new sodium transport decarboxylase. Methylmalonyl–CoA decarboxy-lase from Veillonella alcalescens. Eur. J. Biochem.
132:579–587.
44. Buckel, W., and R. Semmler. 1983. Purifi cation, characterization and reconstitution of glutaconyl–
CoA decarboxylase. Eur. J. Biochem. 136:427–434.
45. Schink, B., and N. Pfennig. 1982. Propionigenium modestum gen. nov. sp. nov. A new strictly anaerobic nonsporing bacterium growing on succinate. Arch.
Microbiol. 133:209–216.
46. Hilpert, W., B. Schink, and P. Dimroth. 1984.
Life by a new decarboxylation-dependent energy conservation mechanism with Na+ as coupling ion.
EMBO J. 3:1665–1670.
47. De Vries, W., R. Theresia, M. Rietveld-Struijk, and A. H. Stouthamer. 1977. ATP formation asso-ciated with fumarate and nitrate reduction in grow-ing cultures of Veillonella alcalescens. Antonie van Leeuwenhoek 43:153–167.
48. Buckel, W., and R. Semmler. 1982. A biotin-de-pendent sodium pump: glutaconyl–CoA decarboxy-lase from Acidaminococcus fermentans. FEBS Lett.
148:35–38.
49. Inside-out vesicles are prepared by sonicating whole cells or shearing them with a French pres-sure cell. Right-side-out vesicles are prepared by fi rst removing the cell wall with lysozyme in a hypertonic medium, and then osmotically lysing the protoplasts or spheroplasts in hypotonic medium.
50. Anantharam, V., M. J. Allison, and P. C.
Maloney. 1989. Oxalate:formate exchange. J. Biol.
Chem. 264:7244–7250.
51. Baetz, A. L., and M. J. Allison. 1990. Purifi cation and characterization of oxalyl–coenzyme A decar-boxylase from Oxalobacter formigenes. J. Bacteriol.
171:2605–2608.
52. Baetz, A. L., and M. J. Allison. 1990. Purifi cation and characterization of formyl–coenzyme A trans-ferase from Oxalobacter formigenes. J. Bacteriol.
171:3537–3540.
53. Ruan, Z., V. Anantharam, I. T. Crawford, S. V. Ambudkar, S. Y. Rhee, M. J. Allison, and P.
C. Maloney. 1992. Identifi cation, purifi cation, and reconstitution of OxIT, the oxalate:formate antiport protein of Oxalobacter formigenes. J. Biol. Chem.
267:10537–10543.
33. Reviewed in: Skulachev, V. P. 1992. Chemiosmotic systems and the basic principles of cell energetics, pp.
37–73. In: Molecular Mechanisms in Bioenergetics.
Ernster, L. (Ed.). New Comprehensive Biochemistry:
Molecular Mechanisms in Bioenergetics, Vol. 23.
Elsevier, Amsterdam.
34. Tokuda, H., and T. Unemoto. 1982. Character-ization of the respiration-dependent Na+ pump in the marine bacterium Vibrio alginolyticus. J. Biol.
Chem. 257:10007–10014.
35. Maloney, P. C., and F. C. Hansen III. 1982.
Stoichiometry of proton movements coupled to ATP synthesis driven by a pH gradient in Streptococcus lactis. J. Membrane Biol. 66:63–75.
36. In his review of primary sodium ion translo-cating enzymes, Dimroth points out that V. algi-nolyticus has two different NADH:ubiquinone oxidoreductases: NQR1, which is Na+ dependent and functions at pH 8.5 but not at pH 6.5, and NQR2, which is Na+ independent and is not a cou-pling site. There is apparently no H+-dependent NADH:ubiquinone oxidoreductase. However, these bacteria do have a cytochrome bo oxidase that oxi-dizes the quinol, is not Na+ dependent, and is believed to be a proton pump as in other bacteria. The pres-ence of both pumps can explain how V. alginolyti-cus operates a Na+-dependent respiratory pump at pH 8.5 and a H+-dependent respiratory pump at pH 6.5. The cytochrome bo proton pump must function at both acidic and basic pH values because mutants lacking the Na+-dependent NADH:ubiquinone oxi-doreductase extrude Na+ at pH 8.5, using a Na+/H+ antiporter in combination with a primary proton pump, and the wild type is known to extrude Na+ at pH 6.5, using the Na+/H+ antiporter in combination with the primary proton pump. (Dimroth, P. 1997.
Primary sodium ion translocating enzymes. Biochim.
Biophys. Acta 1318:11–51.)
37. Kreke, B., and H. Cypionka. 1994. Role of sodium ions for sulfate transport and energy metab-olism in Desulfovibrio salexigens. Arch. Microbiol.
161:55–61.
38. Many nonfermenting anaerobic bacteria carry out electron transport by using as electron accep-tors either organic compounds such as fumarate or inorganic compounds such as nitrate. Thus, electron fl ow in these bacteria can be coupled to proton effl ux and the establishment of a ∆p. Furthermore, even fermenting bacteria can carry out some fumarate res-piration generating a ∆p. However, the major source of energy for the ∆p in most fermenting bacteria is ATP hydrolysis.
39. Dimroth, P. 1997. Primary sodiumion translocat-ing enzymes. Biochim. Biophys. Acta 1318:11–51.
40. Dimroth, P. 1990. Energy transductions by an electrochemical gradient of sodium ions, pp. 114–
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growing and nongrowing cells of Streptococcus cre-moris. J. Bacteriol. 162:383–390.
65. Oesterhelt, D., and J. Tittor. 1989. Two pumps, one principle: light-driven ion transport in halobac-teria. Trends Biochem. Sci. 14:57–61.
66. Bogomolni, R. A., R. A. Baker, R. H. Lozier, and W. Stoeckenius. 1980. Action spectrum and quan-tum effi ciency for proton pumping in Halobacterium halobium. Biochemistry 19:2152–2159.
67. Henderson, R., J. M. Baldwin, and T. A. Ceska.
1990. Model for the structure of bacteriorhodopsin based on high-resolution electron cryomicroscopy.
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68. The extreme halophiles require unusually high external NaCl concentrations [at least 3–5 M (i.e., 17–28%)] to grow. They inhabit hypersaline envi-ronments such as the solar salt evaporation ponds near San Francisco and salt lakes (e.g., the Great Salt Lake in Utah and the Dead Sea). There are now six recognized genera, two of them being the well-known Halobacterium and Halococcus. The best studied is Hb. salinarium (halobium). The other four genera are Haloarcula, Haloferax, Natronobacterium, and Natronococcus. The majority of the known halo-philic archaea are aerobic chemo-organotrophs and can grow on simple carbohydrates as well as long-chain saturated hydrocarbons. They generally grow best at pH values between 8 and 9. However, Natronobacterium and Natronococcus are also alka-liphilic and grow well at pH values up to 11. When oxygen is not present, the halobacteria will grow anaerobically by using several electron acceptors in place of oxygen. These include fumarate, dimethyl sulfoxide (DMSO), and trimethylamine N-oxide (TMAO). Members of the genera Haloarcula and Haloferax can grow on nitrate as the terminal elec-tron acceptor. Some of the halobacteria reduce the nitrate to nitrite and some reduce it completely to nitrogen gas. Some halobacteria can also grow fer-mentatively in the absence of oxygen. These include Hb. salinarium (halobium), which can ferment argi-nine to citrulline.
69. Oesterhelt, D., and G. Krippahl. 1983.
Phototrophic growth of halobacteria and its use for isolation of photosynthetically defi cient mutants.
Ann. Microbiol. (Inst. Pasteur). 134B:137–150.
70. Gest, H. 1993. Photosynthetic and quasi-photo-synthetic bacteria. FEMS Microbiol. Lett. 112:1–6.
71. Some halophilic archaea can use nitrate as an electron acceptor to carry out anaerobic respiration.
72. Respiration can be severely limited under cer-tain growth conditions because the oxygen content of hypersaline waters, the normal habitat of these organisms, is usually 20% or less than is found in normal seawater, and in unstirred ponds oxygen becomes even more scarce. The halobacteria can derive energy from the fermentation of amino acids;
but in the absence of a fermentable carbon source and respiration, light is the only source of energy.
54. To prepare proteoliposomes, one disperses phos-pholipids (e.g., those isolated from E. coli) in water, where they spontaneously aggregate to form spheri-cal vesicles consisting of concentric layers of phos-pholipid. These vesicles, called liposomes, are then subjected to high-frequency sound waves (sonic oscillation), which break them into smaller vesicles surrounded by a single phospholipid bilayer resem-bling the lipid bilayer found in natural membranes.
Then purifi ed protein (e.g., the OxIT antiporter) is mixed with the sonicated phospholipids in the pres-ence of detergent, and the suspension is diluted into buffer. The protein becomes incorporated into the phospholipid bilayer, and membrane vesicles called proteoliposomes are formed. When the proteoli-posomes are incubated with solute, they catalyze uptake of the solute into the vesicles, provided the appropriate carrier protein has been incorporated. In addition, one can “load” the proteoliposomes with solutes (e.g., oxalate) by including these in the dilu-tion buffer.
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