On the cellular highway, motor proteins called dyneins rule the road. Dyneins "walk" along structures called microtubules to deliver cellular cargo, such as signaling molecules and organelles, to different parts of a cell. Without dynein on the job, cells cannot divide and people can develop neurological diseases. Now, a new study, which was published on February 7, 2018 in Nature Structural & Molecular Biology, provides the first three-dimensional (3D) visualization of the dynein-dynactin complex bound to microtubules. The article is titled “Cryo-Electron Tomography Reveals That Dynactin Recruits a Team of Dyneins for Processive Motility.” The study leaders from The Scripps Research Institute (TSRI) report that a protein called dynactin hitches two dyneins together, like a yoke locking together a pair of draft horses. "If you want a team of horses to move in one direction, you need to line them up," says Gabriel C. Lander, PhD, a TSRI Associate Professor and senior author of the study. "That's exactly what dynactin is doing to dynein molecules." Understanding how the dynein-dynactin complex is assembled and organized provides a critical foundation to explain the underlying causes of several dynein-related neurodegenerative diseases such as spinal muscular atrophy (SMA) and Charcot-Marie-Tooth (CMT) disease. Researchers knew that dynactin is required for dynein to move cargo, but they struggled to get a complete picture of how the different parts of the complex worked together. "We knew that dynein only becomes active when it binds with a partner called dynactin. The problem was that, historically, it was difficult to solve this structure because it is very flexible and dynamic," explains Danielle Grotjahn, a TSRI graduate student and co-first author of the study.
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