Structural highlights
Publication Abstract from PubMedMicrotubules are a hallmark of eukaryotes. Archaeal and bacterial homologs of tubulins typically form homopolymers and non-tubular superstructures. The origin of heterodimeric tubulins assembling into microtubules remains unclear. Here, we report the discovery of microtubule-forming tubulins in Asgard archaea, the closest known relatives of eukaryotes. These Asgard tubulins (AtubA/B) are closely related to eukaryotic alpha/beta-tubulins and the enigmatic bacterial tubulins BtubA/B. Proteomics of Candidatus Lokiarchaeum ossiferum showed that AtubA/B were highly expressed. Cryoelectron microscopy structures demonstrate that AtubA/B form eukaryote-like heterodimers, which assembled into 5-protofilament bona fide microtubules in vitro. The additional paralog AtubB2 lacks a nucleotide-binding site and competitively displaced AtubB. These AtubA/B2 heterodimers polymerized into 7-protofilament non-canonical microtubules. In a sub-population of Ca. Lokiarchaeum ossiferum cells, cryo-tomography revealed tubular structures, while expansion microscopy identified AtubA/B cytoskeletal assemblies. Our findings suggest a pre-eukaryotic origin of microtubules and provide a framework for understanding the fundamental principles of microtubule assembly. Microtubules in Asgard archaea.,Wollweber F, Xu J, Ponce-Toledo RI, Marxer F, Rodrigues-Oliveira T, Possnecker A, Luo ZH, Malit JJL, Kokhanovska A, Wieczorek M, Schleper C, Pilhofer M Cell. 2025 Mar 19:S0092-8674(25)00254-5. doi: 10.1016/j.cell.2025.02.027. PMID:40120574[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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