This research unveils that Asgard archaea rhodopsins uniquely utilize diverse xanthophyll antennas like lutein and fucoxanthin to capture light, potentially enhancing energy production in these microorganisms and offering insights into early life forms.
Scientists have discovered that HeimdallRs, a type of rhodopsin found in 'Ca. Kariarchaeum', can bind to various xanthophylls, including lutein and fucoxanthin. This is unlike other archaeal proton pumps, which either cannot bind carotenoids or have limited binding capabilities. This unique ability suggests that these archaea might scavenge these light-harvesting molecules from their environment.
Researchers selected three HeimdallR proteins (HeimdallR1, HeimdallR2, and HeimdallR3) based on their sequence differences. They also chose ACB-G35 as a representative of Archaea clade B rhodopsins. These proteins were studied to understand how they interact with different light-sensitive molecules.
The study involved detailed analysis of the genomes of 'Ca. K. pelagium' strains to understand their genetic makeup. Phylogenetic reconstruction, a method of tracing evolutionary relationships, was used to place HeimdallR3 within the 'Ca. Kariarchaeaceae' family. This helped to understand the evolutionary context of these light-sensitive proteins.
Experiments showed that HeimdallRs possess a canonical fenestration, a structural feature similar to carotenoid-binding proteorhodopsins. This allows them to utilize xanthophyll antennas. Unlike other archaeal rhodopsins, HeimdallRs can use a variety of xanthophylls, possibly reflecting their ability to recruit these molecules from their surroundings.
The discovery that HeimdallRs can utilize different xanthophylls provides insights into the light-harvesting strategies of these archaea. Understanding how these tripartite complexes assemble could offer valuable knowledge about microbial energy production. This research highlights the adaptability of archaea in utilizing available resources in their environment.