title: Crenactin forms actin-like double helical filaments regulated by arcadin-2.
abstract: The similarity of eukaryotic actin to crenactin, a filament-forming protein from the crenarchaeonPyrobaculum calidifontissupports the theory of a common origin of Crenarchaea and Eukaryotes. Monomeric structures of crenactin and actin are similar, although their filament architectures were suggested to be different. Here we report that crenactin formsbona fidedouble helical filaments that show exceptional similarity to eukaryotic F-actin. With cryo-electron microscopy and helical reconstruction we solved the structure of the crenactin filament to 3.8 Å resolution. When forming double filaments, the 'hydrophobic plug' loop in crenactin rearranges. Arcadin-2, also encoded by the arcade gene cluster, binds tightly with its C-terminus to the hydrophobic groove of crenactin. Binding is reminiscent of eukaryotic actin modulators such as cofilin and thymosin β4 and arcadin-2 is a depolymeriser of crenactin filaments. Our work further supports the theory of shared ancestry of Eukaryotes and Crenarchaea.
authors.affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, United Kingdom.
authors.forename: Thierry
authors.initials: T
authors.lastname: Izoré
authors.affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, United Kingdom.
authors.forename: Danguole
authors.initials: D
authors.lastname: Kureisaite-Ciziene
authors.affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, United Kingdom.
authors.forename: Stephen H
authors.identifier: 0000-0001-9135-6253
authors.initials: SH
authors.lastname: McLaughlin
authors.affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge, United Kingdom.
authors.forename: Jan
authors.identifier: 0000-0002-5218-6615
authors.initials: J
authors.lastname: Löwe
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry* / Q000648:ultrastructure; D051339:Actin Depolymerizing Factors / Q000737:chemistry* / Q000648:ultrastructure; D000199:Actins / Q000737:chemistry* / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000235:genetics*; D020285:Cryoelectron Microscopy; D003599:Cytoskeleton / Q000737:chemistry / Q000648:ultrastructure; D008840:Microfilament Proteins / Q000737:chemistry / Q000235:genetics* / Q000648:ultrastructure; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D041543:Pyrobaculum / Q000737:chemistry
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; D001426:Bacterial Proteins; D008840:Microfilament Proteins
keywords: Crenarchaea; F-actin; MreB; Pyrobaculum calidifontis; arcade cluster; bacterial cytoskeleton; biophysics; cell biology; structural biology