Cryo-EM Structure of Actin Filaments from Zea mays Pollen

Actins are among the most abundant and conserved proteins in eukaryotic cells, where they form filamentous structures that perform vital roles in key cellular processes. Although large amounts of data on the biochemical activities, dynamic behaviors, and important cellular functions of plant actin filaments have accumulated, their structural basis is elusive. Here, we report a 3.9 Å structure of the plant actin filament (ZMPA) from Zea mays pollen using cryo-electron microscopy. The structure shows a right-handed, double-stranded (two strands running parallel to each other) and staggered architecture that is stabilized by intra- and interstrand interactions. While the overall structure resembles that of other actin filaments, its DNase I-binding loop (D-loop) bends further outward, adopting an open conformation similar to that of the jasplakinolide- or Beryllium fluoride (BeFx)-stabilized rabbit skeleton muscle actin (RSMA) filament. Single-molecule magnetic tweezer analysis revealed th...