Genomes of Asgard archaea encode profilins that regulate actin

Area of Science:

• Cell Biology
• Evolutionary Biology
• Microbiology

Background:

• The origin of eukaryotic cells remains a significant scientific question.
• Metagenomics suggests a link between Archaea and eukaryotes, with Asgard archaea showing eukaryotic gene homologues.
• The functional relevance of these archaeal homologues is not fully understood.

Purpose of the Study:

• To investigate the presence and function of profilins in Asgard archaea.
• To determine if Asgard archaea possess a regulated actin cytoskeleton.
• To understand the evolutionary history of actin-cytoskeleton components.

Main Methods:

• Biochemical analysis of profilin proteins from Asgard archaea (Loki, Odin, Heimdall).
• Interaction studies with mammalian and rabbit actin.
• Actin polymerization and nucleation assays in the presence of archaeal profilins and phospholipids.

Main Results:

• Asgard archaea encode functional profilins that interact with actin.
• These archaeal profilins regulate actin polymerization and nucleation, suggesting a primordial actin system.
• Asgard profilins do not interact with polyproline motifs, indicating this interaction evolved later in eukaryotes.

Conclusions:

• Asgard archaea possess a regulated actin cytoskeleton, a key eukaryotic feature.
• This finding supports the hypothesis of eukaryotic cell origins within Archaea.
• The archaeal actin system may be membrane-associated and primordial, predating complex eukaryotic cytoskeletal functions.