Dynein c from Chlamydomonas flagella inner arms
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Model of dynein and its power stroke
The stem is shown attached to a substrate. It is bent at the narrow neck, and continues across the rear face of the head as the linker. It joins the first of six AAA domains that have been identified in dynein sequences. The first four of these bind nucleotide. The last two probably don't, and are shown grey. The C-terminal part of the dynein heavy chain has an unknown fold, and is illustrated as a black blob. Between AAA4 and AAA5, the antiparallel coiled coil stalk carries the microtubule-binding domain at its tip. The microtubule is not drawn to scale.
The power stroke is envisioned to start by the tip of the stalk increasing its affinity for the microtubule, inducing a change in the coiled coil that is fed round the ring of AAA domains to accelerate product release from AAA1. We suggest the message is relayed by a concerted slewing of these AAA domains. As a consequence of the rigid coupling of the linker to AAA1, the head rotates relative to the linker, swinging the stalk anticlockwise, and translating the microtubule about 15 nm to the left (thereby moving the dynein towards the minus end of the microtubule). The model shows what would happen under zero load conditions.