9KCF

Bovine Flagellar TRiC

Summary for 9KCF

• Entry DOI: 10.2210/pdb9kcf/pdb
• EMDB information: 62249
• Descriptor: Probable T-complex protein 1 subunit zeta-2, MAGNESIUM ION, ADENOSINE-5'-DIPHOSPHATE, ... (11 entities in total)
• Functional Keywords: tric, sperm, flagella, motile cilia, chaperone
• Biological source: Bos taurus (domestic cattle); More
• Total number of polymer chains: 16
• Total formula weight: 950187.86

Authors

Cong, Y.,Meng, X. (deposition date: 2024-11-01, release date: 2026-04-29)

Primary citation

Meng, X.,Li, L.,Lin, C.,Zhu, Y.,Feng, Y.,Zhao, Q.,Zhao, N.,Zhou, X.,Tong, Y.,Wang, S.,Yin, G.,Liu, R.,Zhang, L.,Sun, F.,Yan, X.,Zhu, X.,Cong, Y.
Chaperonin TRiC bridges radial spokes for folding locally translated proteins to sustain mammalian sperm flagellar motility.
Mol.Cell, 86:1327-1344.e10, 2026

PubMed Abstract: As animals evolved from external to internal fertilization, sperm flagella, once transiently propelling sperm in water to reach nearby eggs, developed to beat for days in the viscous female reproductive tract. How flagella are remodeled accordingly remains unclear. Unlike externally fertilizing zebrafish and sea urchins, mammalian flagella feature a barrel between radial spokes (RSs) RS1 and RS2. Here, we show that this RS1-RS2 barrel (RRB) is a unique T-complex protein-1 ring complex (TRiC) that folds locally translated polypeptides to sustain flagellar motility. Cryo-electron microscopy (cryo-EM) reveals a flagellum-specific TRiC structure. An in situ cryo-electron tomography (cryo-ET) map of flagellar axonemes captures the RRB TRiC in an active, substrate-receptive state, with additional densities suggestive of folding substrates and cofactors. Mammalian flagella contain components of translation machineries and locally synthesize proteins. Cross-linking mass spectrometry identifies candidate locally translated axonemal proteins and folding substrates. Furthermore, a TRiC ATPase inhibitor markedly represses mouse sperm motility. Our findings provide insights into flagellar remodeling in internally fertilizing species.

PubMed: 41932310
DOI: 10.1016/j.molcel.2026.03.005

Experimental method

ELECTRON MICROSCOPY (3.4 Å)