Formation of an ATP-dependent Microtubule-Neurofilament Complex In Vitro

Neurofilaments are the intermediate filaments of neurons. In mammals they are approximately 10 nm in diameter and are composed primarily of three proteins called the neurofilament triplet with molecular weights of approximately 68,000, 160,000, and 210,000 (Hoffman and Lasek 1975; Lasek and Hoffman 1976; Schlaepfer 1977, 1978; Liem et al. 1978; Micko and Schlaepfer 1978). Recent work of Willard and Simon (1981) makes it appear likely that the 68,000-m.w. protein forms the central core of the filament and that the larger proteins surround it. Neurofilaments are often found in the same regions of neurites as microtubules are and they are most frequently aligned parallel to them (Peters et al. 1976). Recent stereoscopic electron microscopy of invertebrate axons (Hodge and Adelman 1980; Rice et al. 1980) reveals an extensive network of cross bridges between microtubules and neurofilaments, apparently corresponding to the appearance in thin sections of mammalian nerve of wispy side...