Abstract
The electrogenic transport of ATP and ADP by the mitochondrial ADP/ATP carrier (AAC) was investigated by recording transient currents with two different techniques for performing concentration jump experiments: 1) the fast fluid injection method: AAC-containing proteoliposomes were adsorbed to a solid supported membrane (SSM), and the carrier was activated via ATP or ADP concentration jumps. 2) BLM (black lipid membrane) technique: proteoliposomes were adsorbed to a planar lipid bilayer, while the carrier was activated via the photolysis of caged ATP or caged ADP with a UV laser pulse. Two transport modes of the AAC were investigated, ATP(ex)-0(in) and ADP(ex)-0(in). Liposomes not loaded with nucleotides allowed half-cycles of the ADP/ATP exchange to be studied. Under these conditions the AAC transports ADP and ATP electrogenically. Mg(2+) inhibits the nucleotide transport, and the specific inhibitors carboxyatractylate (CAT) and bongkrekate (BKA) prevent the binding of the substrate. The evaluation of the transient currents yielded rate constants of 160 s(-1) for ATP and >/=400 s(-1) for ADP translocation. The function of the carrier is approximately symmetrical, i.e., the kinetic properties are similar in the inside-out and right-side-out orientations. The assumption from previous investigations, that the deprotonated nucleotides are exclusively transported by the AAC, is supported by further experimental evidence. In addition, caged ATP and caged ADP bind to the carrier with similar affinities as the free nucleotides. An inhibitory effect of anions (200-300 mM) was observed, which can be explained as a competitive effect at the binding site. The results are summarized in a transport model.
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- Borlinghaus R., Apell H. J., Läuger P. Fast charge translocations associated with partial reactions of the Na,K-pump: I. Current and voltage transients after photochemical release of ATP. J Membr Biol. 1987;97(3):161–178. doi: 10.1007/BF01869220. [DOI] [PubMed] [Google Scholar]
- Broustovetsky N., Bamberg E., Gropp T., Klingenberg M. Biochemical and physical parameters of the electrical currents measured with the ADP/ATP carrier by photolysis of caged ADP and ATP. Biochemistry. 1997 Nov 11;36(45):13865–13872. doi: 10.1021/bi971578x. [DOI] [PubMed] [Google Scholar]
- Brustovetsky N., Becker A., Klingenberg M., Bamberg E. Electrical currents associated with nucleotide transport by the reconstituted mitochondrial ADP/ATP carrier. Proc Natl Acad Sci U S A. 1996 Jan 23;93(2):664–668. doi: 10.1073/pnas.93.2.664. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Dancsházy Z., Karvaly B. Incorporation of bacteriorhodopsin into a bilayer lipid membrane; a photoelectric-spectroscopic study. FEBS Lett. 1976 Dec 15;72(1):136–138. doi: 10.1016/0014-5793(76)80829-0. [DOI] [PubMed] [Google Scholar]
- Fendler K., Grell E., Bamberg E. Kinetics of pump currents generated by the Na+,K+-ATPase. FEBS Lett. 1987 Nov 16;224(1):83–88. doi: 10.1016/0014-5793(87)80427-1. [DOI] [PubMed] [Google Scholar]
- Fendler K., Jaruschewski S., Hobbs A., Albers W., Froehlich J. P. Pre-steady-state charge translocation in NaK-ATPase from eel electric organ. J Gen Physiol. 1993 Oct;102(4):631–666. doi: 10.1085/jgp.102.4.631. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Klingenberg M. The ADP-ATP translocation in mitochondria, a membrane potential controlled transport. J Membr Biol. 1980 Sep 30;56(2):97–105. doi: 10.1007/BF01875961. [DOI] [PubMed] [Google Scholar]
- Knoll W., Stark G. Temperature-jump experiments on thin lipid membranes in the presence of valinomycin. J Membr Biol. 1977 Oct 3;37(1):13–28. doi: 10.1007/BF01940921. [DOI] [PubMed] [Google Scholar]
- Krämer R. Reconstitution of ADP/ATP translocase in phospholipid vesicles. Methods Enzymol. 1986;125:610–618. doi: 10.1016/s0076-6879(86)25049-1. [DOI] [PubMed] [Google Scholar]
- Nagel G., Fendler K., Grell E., Bamberg E. Na+ currents generated by the purified (Na+ + K+)-ATPase on planar lipid membranes. Biochim Biophys Acta. 1987 Jul 23;901(2):239–249. doi: 10.1016/0005-2736(87)90120-9. [DOI] [PubMed] [Google Scholar]
- Nørby J. G., Esmann M. The effect of ionic strength and specific anions on substrate binding and hydrolytic activities of Na,K-ATPase. J Gen Physiol. 1997 May;109(5):555–570. doi: 10.1085/jgp.109.5.555. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Pfaff E., Klingenberg M. Adenine nucleotide translocation of mitochondria. 1. Specificity and control. Eur J Biochem. 1968 Oct 17;6(1):66–79. doi: 10.1111/j.1432-1033.1968.tb00420.x. [DOI] [PubMed] [Google Scholar]
- Pintschovius J., Fendler K. Charge translocation by the Na+/K+-ATPase investigated on solid supported membranes: rapid solution exchange with a new technique. Biophys J. 1999 Feb;76(2):814–826. doi: 10.1016/S0006-3495(99)77245-0. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Weidemann M. J., Erdelt H., Klingenberg M. Effect of bongkrekic acid on the adenine nucleotide carrier in mitochondria: tightening of adenine nucleotide binding and differentiation between inner and outer sites. Biochem Biophys Res Commun. 1970 May 11;39(3):363–370. doi: 10.1016/0006-291x(70)90585-1. [DOI] [PubMed] [Google Scholar]
- Wulf R., Kaltstein A., Klingenberg M. H+ and cation movements associated with ADP, ATP transport in mitochondria. Eur J Biochem. 1978 Jan 16;82(2):585–592. doi: 10.1111/j.1432-1033.1978.tb12054.x. [DOI] [PubMed] [Google Scholar]