Self‐assembling protein filaments are at the heart of cell function. Among them, tubulin‐like proteins are essential for cell division, DNA segregation and cytoskeletal functions across the domains of life. FtsZ and tubulin share their core structures, a characteristic nucleotide‐binding pocket and similar protofilament architecture. GTP hydrolysis between consecutive subunits drives their assembly dynamics. Two recent studies provide previously missing, filament atomic structures of bacterial FtsZ and a recently discovered archaeal tubulin in their nucleotide triphosphate‐bound states. Both filament structures reveal strikingly conserved interfacial GTPase active sites, with Mg²⁺ and K⁺/Na⁺ cations and an NxDxxD/E triad of catalytic residues, probably inherited from the common ancestor of FtsZs and tubulins. Moreover, both proteins exhibit nucleotide‐regulated subunit association mediated by interfacial water bridges, as well as polymerization‐induced structural changes, likely enabling related dynamic assembly mechanisms.