Cryoatomic force microscopy of filamentous actin.
Cryoatomic force microscopy (cryo-AFM) was used to image phalloidin-stabilized actin filaments adsorbed to mica. The single filaments are clearly shown to be right-handed helical structures with a periodicity of approximately 38 nm. Even at a moderate concentration ( approximately 10 microg/ml), narrow, branched rafts of actin filaments and larger aggregates have been observed. The resolution achieved is sufficient to resolve actin monomers within the filaments. A closer examination of the images shows that the branched rafts are composed of up to three individual filaments with a highly regular lateral registration with a fixed axial shift of approximately 13 nm. The implications of these higher-order structures are discussed in terms of x-ray fiber diffraction and rheology of actin gels. The cryo-AFM images also indicate that the recently proposed model of left-handed F-actin is likely to be an artifact of preparation and/or low-resolution AFM imaging.
Shao
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Department of Molecular Physiology and Biological Physics, Health Sciences Center, University of Virginia, Charlottesville, Virginia 22908-0011 USA.
Shi
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Somlyo
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D008841:Actin Cytoskeleton / Q000648:ultrastructure*; D000199:Actins / Q000648:ultrastructure*; D000538:Aluminum Silicates; D000818:Animals; D018625:Microscopy, Atomic Force; D018482:Muscle, Skeletal / Q000648:ultrastructure; D011817:Rabbits; D014961:X-Ray Diffraction
D000199:Actins; D000538:Aluminum Silicates; C011934:mica