ISSN:
1432-1424
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary Biomembranes are the major site of energy transduction. The chemisomotic theory of energy transduction is based on the following four major systems (i) H+-ATPase which is composed of a catalytic portion (F1) and a H+-channel (F o), (ii) electron transport components, (iii) H+-linked porters, and (iv) a H+-impermeable lipid bilayer which is plugged through by systemsi toiii that are specially oriented to translocate H+. Studies on the molecular mechanism of energy transduction have been hampered by the impurity, instability and complexity of preparations of membrane proteins from mesophilic organism. However, using stable, simple membrane proteins from a thermophilic bacterium, we obtained the following results: 1) Thermophilic H+-ATPase was dissociated into 5 subunits ofF 1 and 3 subunits ofF o and their functions and structures were studied by reconstitution.F 1 was crystallized. 2) Thermophilic cytochrome oxidase, cytochromec and NADH-dehydrogenase were purified. In contrast to the complex mitochondrial cytochrome oxidase (7 subunits) and NADH-dehydrogenase (3 subunits), the purified thermophilic proteins were shown to be composed of single components. 3) H+-linked porters such as a H+-driven amino acid carrier and a Na+-H+ antiporter were characterized. 4) Thermophilic lipids were shown to be completely saturated. Using these stable lipids, liposomes capable of H+-driven vectorial reactions including net ATP synthesis and alanine transport were reconstituted.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01926366
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