Origin of mitochondria by intracellular enslavement of a photosynthetic purple bacterium.
Proc Biol Sci
; 273(1596): 1943-52, 2006 Aug 07.
Article
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| MEDLINE
| ID: mdl-16822756
ABSTRACT
Mitochondria originated by permanent enslavement of purple non-sulphur bacteria. These endosymbionts became organelles through the origin of complex protein-import machinery and insertion into their inner membranes of protein carriers for extracting energy for the host. A chicken-and-egg problem exists selective advantages for evolving import machinery were absent until inner membrane carriers were present, but this very machinery is now required for carrier insertion. I argue here that this problem was probably circumvented by conversion of the symbiont protein-export machinery into protein-import machinery, in three phases. I suggest that the first carrier entered the periplasmic space via pre-existing beta-barrel proteins in the bacterial outer membrane that later became Tom40, and inserted into the inner membrane probably helped by a pre-existing inner membrane protein, thereby immediately providing the protoeukaryote host with photosynthesate. This would have created a powerful selective advantage for evolving more efficient carrier import by inserting Tom70 receptors. Massive gene transfer to the nucleus inevitably occurred by mutation pressure. Finally, pressure from harmful, non-selected gene transfer to the nucleus probably caused evolution of the presequence mechanism, and photosynthesis was lost.
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Banco de datos:
MEDLINE
Asunto principal:
Proteobacteria
/
Evolución Biológica
/
Mitocondrias
Idioma:
En
Año:
2006
Tipo del documento:
Article