title: Visualization of intrinsically disordered regions of proteins by high-speed atomic force microscopy.
abstract: Intrinsically disordered (ID) regions of proteins are recognized to be involved in biological processes such as transcription, translation, and cellular signal transduction. Despite the important roles of ID regions, effective methods to observe these thin and flexible structures directly were not available. Herein, we use high-speed atomic force microscopy (AFM) to observe the heterodimeric FACT (facilitates chromatin transcription) protein, which is predicted to have large ID regions in each subunit. Successive AFM images of FACT on a mica surface, captured at rates of 5-17 frames per second, clearly reveal two distinct tail-like segments that protrude from the main body of FACT and fluctuate in position. Using deletion mutants of FACT, we identify these tail segments as the two major ID regions predicted from the amino acid sequences. Their mechanical properties estimated from the AFM images suggest that they have more relaxed structures than random coils. These observations demonstrate that this state-of-the-art microscopy method can be used to characterize unstructured protein segments that are difficult to visualize with other experimental techniques.
authors.affiliation: Department of Physics, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Miyagi
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Tsunaka
authors.forename: Takayuki
authors.initials: T
authors.lastname: Uchihashi
authors.forename: Kouta
authors.initials: K
authors.lastname: Mayanagi
authors.forename: Susumu
authors.initials: S
authors.lastname: Hirose
authors.forename: Kosuke
authors.initials: K
authors.lastname: Morikawa
authors.forename: Toshio
authors.initials: T
authors.lastname: Ando
mesh_terms: D017353:Gene Deletion; D018625:Microscopy, Atomic Force / Q000379:methods*; D046529:Microscopy, Electron, Transmission; D009154:Mutation / Q000235:genetics; D011506:Proteins / Q000235:genetics / Q000648:ultrastructure*; D013997:Time Factors
chemical_list: D011506:Proteins