National Institutes of Health/National Heart, Lung, and Blood Institute (NIH/NHLBI)
United States
National Institutes of Health/National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIH/NIAMS)
United States
Citation
Journal: Proc Natl Acad Sci U S A / Year: 2025 Title: Biochemical and structural bases for talin ABSs-F-actin interactions. Authors: Christian Biertümpfel / Yurika Yamada / Victor Vasquez-Montes / Thien Van Truong / A King Cada / Naoko Mizuno / Abstract: Focal adhesions (FAs) are large intracellular macromolecular assemblies that play a critical role in cell polarization and migration. Talin serves as a direct connection between integrin receptor and ...Focal adhesions (FAs) are large intracellular macromolecular assemblies that play a critical role in cell polarization and migration. Talin serves as a direct connection between integrin receptor and actomyosin cytoskeleton within FAs. Talin contains three actin-binding sites (ABS1-3) that engage discreetly during the development of FAs, thus acting as a critical player in FA initiation and maturation. However, the molecular basis of the ABS-F-actin interactions remains unknown. Here, we explore interactions of ABSs with F-actin to understand the multivalent behavior of talin. Particularly, the cryo-EM structure of the F-actin-ABS3 complex at 2.9 Å shows ABS3 spanning through two actin monomers along the filament axis, each occupied by the R13 rod subdomain and the DD domain. The dimerization of ABS3 occurs through the DD domain where both protomers interact on the actin surface, and the dimerization of talin to the actin surface is necessary for the engagement to F-actin. The R13 helical bundle is distorted upon binding to F-actin and releases the H1 helix from the rest of the bundle. This phenomenon has also been observed with other tension-sensing proteins like vinculin and α-catenin, highlighting that unfolding is relevant for its force sensing activity. On the contrary, ABS2 (R4R8 subdomains), which is thought to be critical for the maintenance of mature FAs, had multiple F-actin-binding regions within ABS2 and the binding likely occurred by these subdomains running through the surface of F-actin, thus strengthening the interactions upon the maturation of FAs.
Model: Quantifoil R1.2/1.3 / Material: COPPER / Mesh: 200 / Support film - Material: CARBON / Support film - topology: HOLEY / Pretreatment - Type: GLOW DISCHARGE / Pretreatment - Time: 45 sec. / Pretreatment - Atmosphere: AIR / Pretreatment - Pressure: 35.0 kPa
Vitrification
Cryogen name: ETHANE / Chamber humidity: 90 % / Chamber temperature: 277 K / Instrument: FEI VITROBOT MARK IV Details: 3.0 ul sample, blotted for 5 s from both sides with filter paper Whatman No.1.
Details
G-actin was polymerized for 60 min at RT. 90 uM talin fragments were then incubated with 10 uM F-actin for 30 min at RT and ultra-centrifuged at 100,000 x g for 20 minutes at RT
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Electron microscopy
Microscope
TFS KRIOS
Specialist optics
Energy filter - Name: GIF Bioquantum
Image recording
Film or detector model: GATAN K3 BIOCONTINUUM (6k x 4k) / Number grids imaged: 1 / Number real images: 6767 / Average exposure time: 6.6 sec. / Average electron dose: 52.0 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
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