Cryo‐EM Structures of Outer‐arm Dynein Array Bound to Microtubule Doublet Reveal a Mechanism for Motor Coordination

• DOI: 10.1096/fasebj.2021.35.s1.03099
• Publication Date: 2021-06-11T00:31:59Z
• Authors: Qinhui Rao; Yue Wang; Pengxin Chai; Yin‐wei Kuo; Long Han; Renbin Yang; Yuchen Yang; Jonathon Howard; Kai Zhang
• Keywords: Axoneme; Molecular motor; Organelle

Eukaryotic cilia are evolutionarily conserved organelles that responsible for cellular motility, sensory reception, embryonic development and intercellular communication. A typical motile cilium is characterized by its ʹ9 + 2ʹ scaffold, composed of nine microtubule doublets (MTDs), a central pair complex (CPC). Two rows axonemal dyneins, the outer-arm dynein (OAD) inner-arm (IAD), power ciliary beating sliding two adjacent MTDs. OAD key motor protein generates majority mechanical forces required this fundamental process. complete ~1.5-2 megadalton in size contains (mammals) or three (in ciliates algae) heavy chains (HCs), intermediate (ICs) variety light (LCs). Each divided into head region AAA+ rings ATP hydrolysis tail holds together whole complex. The permanently attached to MTD A-tubule, while each HC microtubule-binding domain (MTBD) which binds releases B-tubule depending on nucleotide-binding states. Thousands OADs arrayed axoneme drive rhythmic beat, locally synchronize their conformations coordinate with other. Current understanding mainly based cryo-electron tomography (cryo-ET) suggests indirectly connected via series linker structures. Nevertheless, it largely unclear how arrays formed why array important beat. Furthermore, mechanism underlying coordination remains elusive. We set out reveal shed lights conformational changes linked force generation propagation. use model system T. thermophila biochemical cryo-EM analysis. first discovered dynein, HCs (α-, β- γ-HC), ICs (IC2 IC3) indefinite LCs. reconstitute purified onto mimic native determined structures free bound MTDs (OAD-MTD) different states (MTBS) microscopy (cryo-EM). show binding induces spontaneously adopt parallel conformation, primed formation tail-to-head (TTH) manner. synchronized either state. involves extensive network interactions coordinately remodeled when take one step forward from MTBS-1 MTBS-2. TTH remain nearly unchanged both but need be broken allow MTBS alteration during mechanochemical cycle. Nucleotide treatment OAD-MTD reveals temporarily relaxes interfaces nucleotide cycle downstream OADs. In combination previously reported cryo-ET structures, we propose most detailed other move possible beat