Major component of the striated microtubule-associated fibers (SMAFs; system-I-fibers). Consists of a small non-helical N-terminal domain and a rod domain with a 29 residue repeat pattern based on four heptads followed by a skip residue. This alpha-helical protein is characterized by the ability to form a special segmented coiled coil and to assemble into striated fibers of 2 nm protofilaments (By similarity). Belongs to the SF-assemblin family.