Identification and organization of the components in the isolated microvillus cytoskeleton.

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Abstract
The effects of ATP and deoxycholate (DOC) on the cytoskeletal organization of Triton-demembranated microvilli (MV) isolated from chicken intestine brush borders were examined. Isolated MV are composed of a core of tightly bundled microfilaments from which arms project laterally to the plasma membrane with a 33 nm periodicity. These lateral arms spiral around the core microfilaments as a helix with a 25.degree. pitch. Demembranated MV consist of 4 polypeptides with MW of 110,000, 95,000, 68,000 and 42,000, present in molar ratios of 1.1:1.6:1.3:10.0. After addition of 50 .mu.M ATP and 0.1 mM Mg2+, the cytoskeletons are organized as a tight bundle of microfilaments from which lateral arms are missing. In these ATP-treated cytoskeletons, the 110 kdalton polypeptide is reduced in amount and the 95,000, 68,000 and 42,000 polypeptides are present in a 1.3:1.2:10.0 ratio. After incubation with 0.5% DOC, the core microfilaments are no longer tightly bundled yet the lateral arms remain attached with a distinct 33 nm periodicity. These DOC-treated cytoskeletons are depleted of the 95,000 and 68,000 polypeptides and are composed of the 110,000 and 42,000 polypeptides in a 2:10 molar ratio. The microfilaments may be associated into a core bundle by the 95 and 68 kdalton polypeptides and from this core bundle project the lateral arms composed of the 110 kdalton polypeptide.