Poster Presentation The 48th Lorne Conference on Protein Structure and Function 2023

Expanding diversity of Archaea expands the diversity of the Tubulin Superfamily of proteins (#311)

Stephanie J Nobs 1 2 , Katharine Michie 1 3 , Brendan Burns 1 2 , Paul Curmi 1 4
  1. School of Biotechnology and Biological Sciences, University of New South Wales, Sydney, NSW, Australia
  2. Australian Centre for Astrobiology , University of New South Wales, Sydney, NSW, Australia
  3. Structural Biology Facility - Mark Wainwright Analytical Centre, University of New South Wales, Sydney, NSW, Australia
  4. School of Physics, University of New South Wales, Kensington, NSW, Australia

The Tubulin Superfamily of GTPases is an important cytoskeletal protein family found in all domains of life. The well-known Bacterial and Archaeal homologue, FtsZ, is involved in cell division whilst the tubulin heterodimer in Eukaryotes forms the mitotic spindle necessary for chromosome segregation. The structural and functional evolution of the polymerizing protein, from FtsZ to the tubulin heterodimer, is slowly being unveiled through the discovery of Archaeal homologues such as CetZ in Haloferax volcanii and the ancestral eukaryotic homologue OdinTubulin found encoded in Odinarchaeota; a member of the Asgard Archaea Superphylum. As current metagenomic data suggests that Eukaryotes emerged from the Asgard Archaea, this archaeal Superphylum is an ideal candidate to explore the structural, functional and biochemical diversity of Tubulins that range from prokaryotic Tubulins to eukaryotic-like ones. However, confirming the physiological presence and spread of Tubulin proteins and characterising their functions has remained elusive due to the lack of cultures representative from the Asgard phyla and the limited number of high-quality genomes. In order to unveil further insight into the Asgard Tubulin Superfamily, novel Metagenome Assembled Genomes (MAGs) that were assembled from enrichment cultures containing members of Asgard Superphyla were searched for Tubulin-like GTPases. Multiple novel Tubulin GTPase sequences were uncovered in Asgard MAGs across several phyla (Loki-, Heimdall-, and Thor-archaeota), including putative homologues of characterized members, such as FtsZ1 and FtsZ2. A further five Tubulin-like GTPases were also found across the phyla. In silico protein modelling with AlphaFold2 confirms the structural homology of the canonical tubulin/FtsZ GTP-binding domain of the uncovered proteins alongside novel structural features. Although further work is underway to characterise these Tubulins in vitro and in vitro, this data attests to the unexplored diversity of Tubulin proteins that can give insight into the evolution and divergence of proteins during the emergence of Eukaryotes.

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