When purified muscle actin was mixed with microtubule-associated proteins (MAPs) prepared from brain microtubules assembled in vitro, actin filaments were organized into discrete bundles, 26 nm in diameter. MAP-2 was the principal protein necessary for the formation of the bundles. Analysis of MAP-actin bundle formation by sedimentation and electrophoresis revealed the bundles to be composed of approximately 20% MAP-2 and 80% actin by weight. Transverse striations were observed to occur at 28-nm intervals along negatively stained MAP-actin bundles, and short projections, approximately 12 nm long and spaced at 28-nm intervals, were resolved by high-resolution metal shadowing. The formation of MAP-actin bundles was inhibited by millimolar concentrations of ATP, AMP-PCP (beta, gamma-methylene-adenosine triphosphate), and pyrophosphate but not by AMP, ADP, or GTP. The addition of ATP to a solution containing MAP-actin bundles resulted in the dissociation of the bundles into individual actin filaments; discrete particles, presumably MAP-2, were periodically attached along the splayed filaments. These results demonstrate that MAPs can bind to actin filaments and can induce the reversible formation of actin filament bundles in vitro.
Article| August 01 1981
Microtubule-associated proteins (MAPs) and the organization of actin filaments in vitro.
R F Sattilaro,
R F Sattilaro
W L Dentler
E L LeCluyse
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1981) 90 (2): 467–473.
R F Sattilaro, W L Dentler, E L LeCluyse; Microtubule-associated proteins (MAPs) and the organization of actin filaments in vitro.. J Cell Biol 1 August 1981; 90 (2): 467–473. doi: https://doi.org/10.1083/jcb.90.2.467
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