Abstract
Dyneins are motor proteins responsible for transport in the cytoplasm and the beating of axonemes in cilia and flagella. They bind and release microtubules via a compact microtubule-binding domain (MTBD) at the end of a coiled-coil stalk. We address how cytoplasmic and axonemal dynein MTBDs bind microtubules at near atomic resolution. We decorated microtubules with MTBDs of cytoplasmic dynein-1 and axonemal dynein DNAH7 and determined their cryo-EM structures using helical Relion. The majority of the MTBD is rigid upon binding, with the transition to the high-affinity state controlled by the movement of a single helix at the MTBD interface. DNAH7 contains an 18-residue insertion, found in many axonemal dyneins, that contacts the adjacent protofilament. Unexpectedly, we observe that DNAH7, but not dynein-1, induces large distortions in the microtubule cross-sectional curvature. This raises the possibility that dynein coordination in axonemes is mediated via conformational changes in the microtubule.
Highlights
The dynein family is a group of minus-end directed microtubule motors
The MTBD is connected to the AAA+ ring by an bind to microtubules via a small microtubule-binding domain (MTBD) consisting of 6 antiparallel, coiled-coil stalk, containing helices CC1 and CC2
13-protofilament microtubules were made by polymerizing tubulin in a MES-based buffer (Pierson et al, 1978)
Summary
The dynein family is a group of minus-end directed microtubule motors. The two of cellular cargoes (Reck-Peterson et al, 2018; Roberts et al, 2013). Multiple inner cytoplasmic dyneins (dynein-1 and dynein-2) are involved in long-range movement and outer arm axonemal dyneins power the beating motion in cilia and flagella by family members share a common architecture, based around a heavy chain that consists of a ring of six connected AAA+ subdomains (AAA1-6) with the nucleotide sliding adjacent doublet microtubules past each other (Satir et al, 2014). All dynein contains a cargo-binding tail region and a force-generating motor domain. The MTBD is connected to the AAA+ ring by an bind to microtubules via a small microtubule-binding domain (MTBD) consisting of 6 antiparallel, coiled-coil stalk, containing helices CC1 and CC2. It binds to the microtubule at the tubulin intradimer interface (Carter et al, 2008)
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