basal body C-tubule luminal filament

cellstructuremech:basal_body_c_tubule_luminal_filament · Cytoskeleton · Filament · Proposed

A crescent-shaped proteinaceous filament inside the lumen of a basal-body C-tubule, spanning from protofilament C3 to the C6-C7 junction and occurring in a longitudinally repeated array in the distal half of isolated Chlamydomonas reinhardtii basal bodies. [DOI:10.1038/emboj.2011.460]

Image (not hosted — OTHER): PMC3273388.1:f4

Regional triplet density reconstructions. Panel C shows yellow crescent-shaped filaments inside the blue C-tubule lumen, with C3, C6 and C7 labeled, and their longitudinal repetition. Panel B instead shows the separate exterior hook. Panel A has a 10-nm scale bar; the displayed segment is not the biological array length. CRYO_ET · Chlamydomonas reinhardtii (NCBITaxon:3055) · Sam Li, Jose-Jesus Fernandez, Wallace F Marshall and David A Agard; Figure 4, The EMBO Journal (2012), DOI:10.1038/emboj.2011.460. Copyright 2012 European Molecular Biology Organization; CC BY-NC-ND 3.0 Unported. · OTHER · source: PMC PMC3273388.1:f4 · DOI:10.1038/emboj.2011.460

Part of: ciliary basal body (GO:0036064)

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Canonical examples

NCBITaxon:3055 Chlamydomonas reinhardtii — Distal-half triplet reconstructions from isolated basal bodies; Figure 4C resolves the luminal filament separately from the exterior hook in Figure 4B. This species example does not imply occurrence in every strain or throughout the basal-body length. [DOI:10.1038/emboj.2011.460]

Functions

intraluminal C-tubule linkage — In the characterized Chlamydomonas distal region, the filament spans the C-tubule lumen from protofilament C3 to the C6-C7 junction. This is an observed structural connection, not a demonstrated requirement for stiffness, assembly or motility.
- DOI:10.1038/emboj.2011.460 Longitudinal-variation Results and Figure 4C show crescent-shaped luminal densities. Mechanical reinforcement and contact with the separate exterior hook are proposed interpretations, not tested filament-specific functions.

Physical properties

OTHER: 8 UO:0000018 (Longitudinal spacing of repeated luminal filaments in the distal-half Chlamydomonas reinhardtii basal-body triplet subtomogram average, reported in Figure 4C; not filament length.) [DOI:10.1038/emboj.2011.460]
OTHER: 13.6 UO:0000018 (Approximate span from C3 to the C6-C7 junction in the distal-half Chlamydomonas reinhardtii reconstruction: the reported approximately 136 angstrom value converted to nanometers. Not a measured contour length or the length of the axial array.) [DOI:10.1038/emboj.2011.460]

Discussions

CURATION_TODO (RESOLVED): Separate the luminal filament from neighboring assemblies. A resolved filament is a structural entity even without a molecular assignment. Classification reassessment on 2026-10-11: the previous GO:0005856 is-a parent conflated a subassembly with its containing framework. GO:0005575 is retained conservatively because the inspected density does not establish a protein-complex or polymeric-fiber classification; morphology and basal-body parthood are unchanged.
CURATION_TODO (OPEN): Identify constituents of the C3-to-C6/C7 luminal filament. A density-derived mass does not identify proteins or stoichiometry.
CURATION_TODO (RESOLVED): Keep proposed mechanics and assembly separate from imaging. Regional co-occurrence is neither a direct interaction assay nor a time course.
CURATION_TODO (RESOLVED): Avoid transferring proximal MIP names to the distal filament. C-lumen localization alone does not establish structural identity.
CURATION_TODO (RESOLVED): Distinguish filament dimensions from map metadata. Reconstruction windows and resolution are not biological structure lengths.

Datasets

Chlamydomonas basal-body triplet reconstruction (EMDB:EMD-5252) · OTHER · STRUCTURAL_IMAGING
Organism: Chlamydomonas reinhardtii · Platform: cryo-electron tomography and subtomogram averaging
Released native EMDB metadata links taxon 3055, strain cc3491 and PMID:22157822 to the exact primary DOI. The archive strain label is not evidence of a separately deposited filament map. Whole-triplet mass, component counts and resolution do not specify filament composition or dimensions; no map volume is hosted.

Evidence

DOI:10.1038/emboj.2011.460 Li et al. 2012, PMID:22157822. Official PMC3273388.1 JATS and Figure 4 media checksums verified; longitudinal-variation Results, Discussion, reconstruction Methods and Figure 4 caption inspected. Density morphology and repeat are observed; protein identity, reinforcement and assembly chronology are not established by the static reconstructions. No verbatim snippet is asserted.
DOI:10.7554/eLife.43434 Li et al. 2019. Official PMC6384029.1 JATS checksum verified; proximal-region scope, focused MIP Results, complete Table 1 and the regional-comparison Discussion inspected. These support boundaries against MIP8-MIP11, not an exact molecular assignment to the distal C3-to-C6/C7 filament.

Curation history

2026-10-04T12:07:21Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-10-04T12:10:51Z codex · CURATED_RECORD — Added Chlamydomonas-scoped filament morphology, repeat and span, structural linkage, whole-triplet dataset and link-only Figure 4 provenance. Kept protein identity, mechanics and assembly unresolved and separated the distal filament from proximal MIP assignments.
2026-10-11T09:48:34Z codex · ADDRESS_SAVED_REVIEW — Addressed #2204: Replaced the unsupported cytoskeleton is-a parent with conservative cellular-component classification, retained basal-body parthood and unknown molecular identity, and corrected current classification notes without rewriting original discussion provenance.

Source: data/structures/cytoskeleton/basal_body_c_tubule_luminal_filament.yaml