Abstract
We consider a small vesicle whose membrane transports a ligand L into the vesicle through enzymatic units of type A and transports L out of the vesicle through units of type B. Oxidative phosphorylation in mitochondria provides an example, in which L is H+. The kinetics of the two membrane systems (A and B) are coupled through the concentration of L in the vesicle. This interdependence causes the combined membrane system (A plus B) to simulate a single system whenever the net ligand transport into the vesicle is zero. For example, in oxidative phosphorylation, it was thought for some time that ATP was synthesized by the respiratory chain system (via an "active intermediate"). We give the simplest possible analyses of this kind of coupled system, which is very common, by using two-state enzymes for both A and B above. A numerical example is included that illustrates respiratory control in a qualitative way: although the respiratory chain flux by itself does not depend on ADP concentration, the steady-state flux of the coupled systems (respiratory chain and reverse ATPase) does depend on ADP concentration through the interior ligand (H+) concentration.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Alexandre A., Reynafarje B., Lehninger A. L. Stoichiometry of vectorial H+ movements coupled to electron transport and to ATP synthesis in mitochondria. Proc Natl Acad Sci U S A. 1978 Nov;75(11):5296–5300. doi: 10.1073/pnas.75.11.5296. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Heins M., Hendricks J., Martindale L., Smock S., Stein M., Jacobs J. Attitudes of women and men physicians. Am J Public Health. 1979 Nov;69(11):1132–1139. doi: 10.2105/ajph.69.11.1132. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hill T. L. A proposed common allosteric mechanism for active transport, muscle contraction, and ribosomal translocation. Proc Natl Acad Sci U S A. 1969 Sep;64(1):267–274. doi: 10.1073/pnas.64.1.267. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hill T. L. Analysis of a model for active transport. Proc Natl Acad Sci U S A. 1970 Feb;65(2):409–416. doi: 10.1073/pnas.65.2.409. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hill T. L., Chance B. Steady-state kinetics of models of respiratory chain enzymes with isopotential pools and conformational site enzymes. J Theor Biol. 1978 May 8;72(1):17–56. doi: 10.1016/0022-5193(78)90016-4. [DOI] [PubMed] [Google Scholar]
- Hill T. L. Theoretical study of the effect of enzyme-enzyme interactions on steady-state enzyme kinetics. Proc Natl Acad Sci U S A. 1977 Sep;74(9):3632–3636. doi: 10.1073/pnas.74.9.3632. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hill T. L. Unsymmetrical and concerted examples of the effect of enzyme--enzyme interactions on steady-state enzyme kinetics. Proc Natl Acad Sci U S A. 1978 Mar;75(3):1101–1105. doi: 10.1073/pnas.75.3.1101. [DOI] [PMC free article] [PubMed] [Google Scholar]