ATP induced conformational change of axonemal outer dynein arms studied by cryo-electron tomography

Abstract

Axonemal dyneins in the outer dynein arm (ODA) generate force for ciliary beating. We analyzed three states of ODA during the power stroke cycle using in situ cryo-electron tomography, subtomogram averaging and classification. These states of force generation depict the pre-power stroke, post-power stroke conformations and an intermediate state. Comparison of these conformations to published in vitro atomic structures of cytoplasmic dynein, ODA and Shulin-ODA complex showed that the orientation and position of the dynein head and linker differs. Our analysis shows that all dynein linkers in the in the absence of ATP interact with AAA3/AAA4, indicating interaction to the adjacent B-tubule direct dynein orientation. For the pre-power stroke conformation, we found changes of the tail anchored on the A-tubule. We built pseudo-atomic models from high-resolution structures to generate a best fitting atomic model to the in-situ pre- and post-power stroke ODA, thereby showing that the Shulin-ODA display similar conformation as the active pre-power stroke ODA conformation in the axoneme.