非筋細胞のアクチン

抄録

Movement is one of the fundamental properties of living cells. It is expressed in such diverse cellular activities in animal and plant cells as cytoplasmic streaming, amoeboid movement, phagocytosis, morphogenetic movement, cytokinesis, mitosis, secretory processes and probably the regulation of the topological distribution of membrane proteins as well.
Recently proteins which closely resemble the major contractile proteins of muscle, actin and myosin, have found in most types of eukaryotic cells and even in prokaryotic cells. The universal occurence of these proteins suggests that they provide the basis of a general mechanism for producing cellular movement, of which muscle contraction is a specialized example.
In general the nonmuscle actins (cytoplasmic actins) resemble the muscle actin, and this similarity was mainly emphasized in early researches. However, more extensive biochemical studies have increasingly revealed some differences, especially in microheterogenity among actins. Another significant focus of recent researches concerns the ability of nonmuscle actins to form supramolecular assemblies or higher aggregates corresponding to the microfilament bundles or stress fibers seen in microscopy. These studies suggest that actin may play a cytoskeletal as well as a contractile role in nonmuscle cells.
In this review we have focused our attension to emphasize recent advances in the biochemical understanding of the nonmuscle actin. We discuss the properties of the purified actin and the morphological distribution of actin filaments and its properties. Most of the papers discussed here were published after 1974.