Cytoskeletal functions of cytoplasmic contractile proteins.

This is a review of the evidence that the cytoplasmic contractile proteins function as a cytoskeletal system in the cytoplasmic matrix. Biochemical experiments show that cycoplasmic actin filaments can form a solid gel under conditions likely to exist in living cells. The actin filaments are associated with other proteins which amy stabilize the gel and which are involved with motile force generation like myosin. Ultrastructural studies show that actin filaments are difficult to preserve, but that under stabilizing conditions networks of actin filaments are found throughtout the cytoplasmic matrix.