| Autor: |
Pozzan, T., Virgilio, F. Di, Bragadin, M., Miconi, V., Azzone, G. F. |
| Zdroj: |
Proceedings of the National Academy of Sciences of the United States of America; May 1979, Vol. 76 Issue: 5 p2123-2127, 5p |
| Abstrakt: |
H+/site, charge/site, and ATP/site ratios have been determined at coupling sites I, II, and III. Three e-donors have been used for coupling site III: ferrocyanide, ascorbate + tetramethyl-p-phenylenediamine (TMPD), and succinate + TMPD. The H+/site ratios are 4.0 with ferrocyanide and 6.0 with succinate + TMPD (at pH <7.0); the charge/site ratios are 6.0 with ferrocyanide and with succinate + TMPD (at pH <7.0) and 4.0 with ascorbate + TMPD; the ATP/site ratio is 1.34 with ascorbate + ferrocyanide. These ratios have been obtained in the presence of amounts of antimycin A that provide full inhibition of site II. For coupling sites I and II, ferricyanide has been used as e-acceptor and succinate or NAD-linked substrates as e-donors. The H+/site ratios are 4.0 at sites I and II; the charge/site ratios are 4.0 at site I and 2.0 at site II; the ATP/site ratios are 1.0 at site I and 0.5 at site II. Two major factors affect the stoichiometries: (i) dimension of [unk]Hand (ii) supply of H+from the matrix. There is a correlation between collapse of [unk]Hand increase of H+/site and charge/site ratios. This indicates that approximation of the phenomenologic stoichiometry of the H+pump is obtained when flow ratios are measured at level flow. That charge/site and ATP/site ratios increase when ferrocyanide is e-donor and decrease when ferricyanide is e-acceptor is attributed to the localization of the redox couple. This leads to separation of 1 charge/e-when ferrocyanide is e-donor and to consumption of 1 charge/e-when ferricyanide is e-acceptor. To account for an extrusion of H+in excess of that predicted by the loop model, it is proposed that each coupling site contains a channel acting as a H+pump. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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