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An actin-based cytoskeleton in archaea.
Mol Microbiol. 2011 May; 80(4):1052-61
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23 Jun 2011
Controversial, New Finding
DOI: 10.3410/f.9239956.12510054
This paper reports several important discoveries related to the cytoskeleton in Archaea. Perhaps foremost is the new actin homolog, Crenactin, which appears to be present in all Crenarchaea with a rod or filamentous shape. Like MreB in bacteria, Crenactin forms spiral arrangements in the cells. In a phylogenetic tree, the Crenactins are much closer to eukaryotic actins than any other prokaryotic actins, making them a candidate for the precursor of the eukaryotic actin cytoskeleton.
Crenactin is typically in a gene cluster with four other genes, designated Arcadins. Three of these also make patchy or spiral structures, which may partly overlap Crenactin spirals. The most intriguing is Arcadin-2, which localizes to the center of the cell where cytokinesis should occur. The Thermoproteales lineage, where the Arcadins are mostly found, has no FtsZ (like all Crenarchaea) but also no ESCRT-III, which brings about cytokinesis in most Crenarchaea. Arcadin-2 is, therefore, a candidate for a novel cytokinesis machine.
Disclosures
None declared
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Erickson H: F1000Prime Recommendation of [Ettema TJ et al., Mol Microbiol 2011, 80(4):1052-61]. In F1000Prime, 23 Jun 2011; DOI: 10.3410/f.9239956.12510054. F1000Prime.com/9239956#eval12510054
F1000Prime Recommendations, Dissents and Comments for [Ettema TJ et al., Mol Microbiol 2011, 80(4):1052-61]. In F1000Prime, 19 Jun 2013; F1000Prime.com/9239956
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In eukaryotic and bacterial cells, spatial organization is dependent upon cytoskeletal filaments. Actin is a main eukaryotic cytoskeletal element, involved in key processes such as cell shape determination, mechanical force generation and cytokinesis. We describe an archaeal cytoskeleton which forms helical structures within Pyrobaculum calidifontis cells, as shown by in situ immunostaining. The core components include an archaeal actin homologue, Crenactin, closely related to the eukaryotic counterpart. The crenactin gene belongs to a conserved gene cluster denoted Arcade (actin-related cytoskeleton in Archaea involved in shape determination). The phylogenetic distribution of arcade genes is restricted to the crenarchaeal Thermoproteales lineage, and to Korarchaeota, and correlates with rod-shaped and filamentous cell morphologies. Whereas Arcadin-1, -3 and -4 form helical structures, suggesting cytoskeleton-associated functions, Arcadin-2 was found to be localized between segregated nucleoids in a cell subpopulation, in agreement with possible involvement in cytokinesis. The results support a crenarchaeal origin of the eukaryotic actin cytoskeleton and, as such, have implications for theories concerning the origin of the eukaryotic cell.
© 2011 Blackwell Publishing Ltd.
DOI: 10.1111/j.1365-2958.2011.07635.x
PMID: 21414041
