9631833 de Lanerolle The term "myosin" describes a family of motor proteins that are characterized by their ability to hydrolyze ATP when they bind actin. Myosin II, the most familiar and best characterized member of this family, is a filamentous protein that uses the energy released when ATP is hydrolyzed to move filaments past each other, an essential step in muscle contraction and in cytokinesis. In contrast to our understanding of the physiological properties of myosin II, little is known about the other members of this superfamily, many of which do not form filaments. Of these non-filamentous myosins, myosin I has been studied most extensively. Myosin I was initially described in Acanthamoeba and is now known to be widely distributed in mammalian cells. This protein has been studied extensively at the molecular and biochemical levels, and there is an abundance of information about the cellular distribution of myosin I. The physiological role of this protein, particularly in mammalian cells, is less well defined. In an effort the investigate the physiological role of myosin I in mammalian cells, the protein was purified from bovine adrenal glands and a polyclonal antibody was raised against it. While characterizing these antibodies, it was observed that the affinity-purified antibodies to myosin I stained the nucleus in interphase cells. In light of the recent demonstration by others of actin-like proteins in the nucleus, this data prompted the hypothesis that myosin I is involved in nuclear functions. However, before such a putative role can be investigated, the protein in the nucleus which reacts with the antibody must be unambiguously identified. Therefore, the goal of this research is to purify sufficient protein to identify it by microsequencing it. ***
