Submolecular-scale imaging of ?-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 ?-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 ?-helix backbone (0.54 nm). The identification of individual ?-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.

SUBMITTER: Asakawa H 

PROVIDER: S-EPMC3164191 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature