| 研究実績の概要 |
The origin of the eukaryotic cell is controversial. Metagenomics sequencing has revealed that Asgard archaea genomes contain potential homologs to eukaryotic genes. Several of these gene products are involved in forming the cytoskeleton, a hallmark of eukaryotic cells. Eukaryotic gelsolin superfamily proteins generally comprise three or more related domains. Here we characterize single- and double-domain gelsolins from Thorarchaeota (Thor). Similar domain architectures are present in Heimdall-, Loki-, and Odinarchaeota. Thor gelsolins are functional in regulating rabbit actin in in vitro assays, showing a range of activities including actin filament severing and bundling. These gelsolins bind to the eukaryotic gelsolin/cofilin-binding site on actin. Two-domain, but not one-domain, gelsolins are calcium regulated. Thor gelsolins appear to have the characteristics and structure consistent with primitive gelsolins/cofilins, suggesting that these single- and double-domain gelsolins are a record of a nascent pre-eukaryotic actin-regulation machinery.
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| 今後の研究の推進方策 |
We will further investigate the potential cytoskeletal proteins and membrane regulating proteins encoded in the Asgard metagenomics data: the cytoskeletal proteins tubulins, actins, and proteins involved in trafficking, N-glycosylation, ESCRT complexes, ubiquitination system, and small GTPases. We will use structural biology, biochemistry and cell biology to provide insight as to whether Asgard can be considered as model organisms for the archaea-to-eukaryotic transition. One particular focus will be on the Asgard tubulin. We will determine the structures of Odin tubulin, to assess how far along the evolutionary transition from the prokaryotic cell division protein FtsZ to the eukaryotic microtubule this Asgard tubulin has progressed.
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