Structure of the Sf9 cytoskeletal bundles and hairs projected from the Sf9 cells expressing LSP1. (a) The low magnification micrograph shows a portion from a representative Sf9 cytoskeleton that had produced hairlike projections. Bundles of filaments are found through out the cytoplasm. Large bundles originate in the perinuclear region and, at many points, bundles intersect and/or branch (arrows). Sf9 cells were infected for 48 hours with recombinant huLSP1 baculovirus, attached to coverslips by centrifugation at 280g, Triton X-100 extracted, fixed, rapidly frozen, freeze-dried, and rotary coated with 1.4 nm of tantalum, tungsten, and 2.5 nm of carbon. The bar is 1 μm. (b) Higher magnification of filament bundles. Individual filaments composing the bundles have 10-nm diameters. Some bundle branch points are indicated with arrows. (c) Demonstration that the 10-nm filaments are actin using myosin S1 to decorate them. Bundles are seen to be composed of actin filaments with mixed polarity. Bundles also can contain structures which fail to bind myosin S1 (arrows). The bars in (b) and (c) are 100 nm.