Just like two shy nerds falling in love with the help of a few Romulan ales and a Star Trek movie, sometimes proteins that are destined to be together need some help finding one another. Today’s very cool image is from a paper showing the formation of a processive myosin complex.
Myosin is the molecular motor that walks along actin filaments. The most abundant type of myosin is found in our muscles and is necessary for muscle contraction, yet there are many types of myosin that function in many diverse cell types and processes. Most myosins use their two head domains to “walk” along actin, yet one unusual myosin called Myo4p only has one head domain. Myo4p transports mRNA molecules and forms a complex with an adaptor protein called She3p, yet the Myo4p-She3p complex alone cannot walk on actin. Recently, Krementsova and colleagues reported that another protein called She2p recruits two Myo4p-She3p complexes to form a two-headed motor. She2p serves as the middleman between the two motors and the mRNA that it transports, and provides the entire complex with the ability for long-range and continuous transport of mRNA along actin. In the metal-shadowed electron micrographs above, purified Myo4p-She3p complexes remain single-headed in the absence of She2p (left). In the presence of She2p (right), the Myo4p-She3p motors were able to pair up and form V-shaped structures, indicating a two-headed motor.
Krementsova, E., Hodges, A., Bookwalter, C., Sladewski, T., Travaglia, M., Sweeney, H., & Trybus, K. (2011). Two single-headed myosin V motors bound to a tetrameric adapter protein form a processive complex originally published in The Journal of Cell Biology, 195 (4), 631-641 DOI: 10.1083/jcb.201106146