title: Submolecular-scale imaging of α-helices and C-terminal domains of tubulins by frequency modulation atomic force microscopy in liquid.
abstract: In this study, we directly imaged subnanometer-scale structures of tubulins by performing frequency modulation atomic force microscopy (FM-AFM) in liquid. Individual α-helices at the surface of a tubulin protofilament were imaged as periodic corrugations with a spacing of 0.53 nm, which corresponds to the common pitch of an α-helix backbone (0.54 nm). The identification of individual α-helices allowed us to determine the orientation of the deposited tubulin protofilament. As a result, C-terminal domains of tubulins were identified as protrusions with a height of 0.4 nm from the surface of the tubulin. The imaging mechanism for the observed subnanometer-scale contrasts is discussed in relation to the possible structures of the C-terminal domains. Because the C-terminal domains are chemically modified to regulate the interactions between tubulins and other biomolecules (e.g., motor proteins and microtubule-associated proteins), detailed structural information on individual C-terminal domains is valuable for understanding such regulation mechanisms. The results obtained in this study demonstrate that FM-AFM is capable of visualizing the structural variation of tubulins with subnanometer resolution. This is an important first step toward using FM-AFM to analyze the functions of tubulins.
authors: Bio-AFM Frontier Research Center, Kanazawa University, Kanazawa, Japan.
authors: Hitoshi
authors: H
authors: Asakawa
authors: Koji
authors: K
authors: Ikegami
authors: Mitsutoshi
authors: M
authors: Setou
authors: Naoki
authors: N
authors: Watanabe
authors: Masaru
authors: M
authors: Tsukada
authors: Takeshi
authors: T
authors: Fukuma
mesh_terms: D000818:Animals; D018625:Microscopy, Atomic Force / Q000379:methods*; D008958:Models, Molecular; D057054:Molecular Imaging / Q000379:methods*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013499:Surface Properties; D014404:Tubulin / Q000737:chemistry*
chemical_list: D014404:Tubulin