Myosins are molecular motors that, upon interaction with actin filaments, utilize energy from ATP hydrolysis to generate mechanical force. Each myosin has a conserved N-terminal motor domain that contains both ATP-binding and actin-binding sequences. The myosin-1a protein is expressed by enterocytes, the epithelial cells that line the luminal surface of the small intestine. In these cells the myosin-1a protein localizes specifically to the brush border. Experiments indicate that the brush border population of the encoded protein turns over rapidly, while its head and tail domains interact transiently with the core actin and plasma membrane, respectively. A rapidly exchanging pool of the myosin-1a protein binds to the actin core bundle, which turns over on a much slower timescale.