Identification of the Outer-Inner Dynein Linker as a Hub Controller for Axonemal Dynein Activities

Background: In flagella, the outer dynein arm (ODA) and inner dynein arm (IDA) play distinct roles in generating beating motion. However, functional communications between the two dyneins have not been investigated. Results: Here, we demonstrated by cryo-electron microscopy and chemical crosslinking that intermediate chain 2 (IC2) of ODAs interacts with the dynein regulatory complex in the axoneme and constitutes part of the outer-inner dynein (OID) linker. Furthermore, we identified IC2 as a functional hub between ODAs and IDAs based on the phenotypes of Chlamydomonas mutants expressing biotinylation-tagged IC2. The flagella of the IC2 mutant showed activated microtubule sliding and enhanced ATPase activities of ODAs, as well as an altered waveform, indicating attenuated IDA activity. Conclusions: We concluded that the OID linker controls both ODAs and IDAs and regulates flagellar beating.