In this study I describe the ultrastructural distribution of epinemin (Lawson, D., 1983, J. Cell Biol., 97:1891-1905) in antibody-labelled, helium-cooled, quick-frozen, deep-etched cytoskeletons. This technique reveals that epinemin is expressed asymmetrically at discrete sites on the vimentin core polymer and that usually one (occasionally two or three) antiepinemin molecules are found at each of these discrete foci. Single receptor-bound antiepinemin (IgM) molecules are easily identified in deep-etched cytoskeletons by the use of colloidal gold. Epinemin does not cross-link adjacent intermediate filaments and is not associated with the many 2-3-nm filaments found associated with intermediate filaments in these preparations. The directional changes and interactions undergone by microtubules in taxol-stabilized, antibody-labelled cytoskeletons are also discussed.

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