basal body triplet base

cellstructuremech:basal_body_triplet_base · Cytoskeleton · Other · Proposed

A linker in the proximal region of a microbial ciliary basal body that connects the pinhead to the A-C linker. In Paramecium tetraurelia reconstructions it extends to the ArmB region of the A-C linker. [DOI:10.15252/embj.2020106246]

Paramecium proximal-triplet reconstructions. Panel A shows the triplet base in green connecting the purple pinhead to the turquoise A-C linker at low contour threshold, with an approximate 35-nm span annotation. Panel B uses a higher threshold and shows only a dashed putative triplet-base position; C-F emphasize the neighboring A-C linker and proximal/distal comparisons. These are segmented averages, not raw micrographs or sequence-resolved proteins. CRYO_ET · *Paramecium tetraurelia* (`NCBITaxon:5888`) · Nikolai Klena, Maeva Le Guennec, Anne‐Marie Tassin, Hugo van den Hoek, Philipp S Erdmann, Miroslava Schaffer, Stefan Geimer, Gabriel Aeschlimann, Lubomir Kovacik, Yashar Sadian, et al.; CC BY, via PubMed Central · CC_BY_4_0 · source: PMC PMC7667884.1 embj2020106246-fig-0005 · `DOI:10.15252/embj.2020106246`

Synonyms: centriole triplet base

Part of: ciliary basal body (GO:0036064)

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

Canonical examples

NCBITaxon:5888 Paramecium tetraurelia — Ninefold-symmetrized cryo-ET cross sections and a focused subtomogram average resolve the pinhead-to-A-C-linker connection. Methods describe cortical units isolated from d4-2 and Delta-CenBP1; Figure 5 is not assigned to one strain. The proximal-region analysis used 11 uncompressed tomograms containing 16 centrioles with intact proximal regions. [DOI:10.15252/embj.2020106246]
NCBITaxon:3055 Chlamydomonas reinhardtii — In situ cryo-ET of FIB-milled mat3-4 cells and ninefold-symmetrized cross sections show the link in Figure 4. The Paramecium focused-map measurement is not transferred to this species. [DOI:10.15252/embj.2020106246]

Functions

ciliary basal body organization GO:0032053 — Provides a structural connection between the pinhead and A-C linker in the imaged proximal region. This is an observed spatial arrangement, not proof of a mechanical stiffness, essentiality or assembly time course.
- DOI:10.15252/embj.2020106246 Figures 4 and 5 and the accompanying Results identify the connecting density; the Paramecium average locates its A-C-linker contact on ArmB.

Physical properties

LENGTH: 35 UO:0000018 (Approximate pinhead-to-A-C-linker span annotated as about 35 nm in the Paramecium tetraurelia proximal-triplet reconstruction, Figure 5A, and described in the Discussion. No replicate distribution or uncertainty is reported for this annotation. It is not an axial repeat or a universal length.) [DOI:10.15252/embj.2020106246]

Discussions

CURATION_TODO (RESOLVED): Keep the triplet base distinct from adjacent basal-body modules. A named linker is not the entire cartwheel, pinhead or A-C linker.
CURATION_TODO (OPEN): Resolve triplet-base molecular composition and a narrower structure class. A proposed coiled-coil assignment is not a demonstrated molecular identity.
CURATION_TODO (RESOLVED): Separate observed connectivity from periodicity and mechanical hypotheses. Low density and static axial differences do not uniquely specify occupancy, flexibility or chronology.

Datasets

Paramecium microtubule triplet from the start of the proximal region (EMDB:EMD-10729) · OTHER · STRUCTURAL_IMAGING
Organism: Paramecium tetraurelia · Platform: cryo-electron tomography and subtomogram averaging
Native released EMDB metadata verifies the start-of-proximal-region title, taxon 5888, DOI and PMID:32954513. The paper lists EMD-10726 through EMD-10729 in Data availability. EMD-10728 denotes the distal comparison; EMD-10726 and EMD-10727 denote A-C-linker-focused maps. Their sample-name fields repeat start-region wording despite different entry titles, so titles are used to distinguish these deposits. No exact structure xref or hosted map volume is asserted.

Evidence

DOI:10.15252/embj.2020106246 Klena et al. 2020, PMID:32954513. Checksum-verified PMC7667884.1 JATS Results, Discussion, species preparation and A-C-linker averaging Methods, Figure 5 and Data availability inspected. Figure 5 was visually inspected; its low-threshold triplet-base density is not a sequence-resolved model.

Curation history

2026-10-04T14:28:41Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-10-04T14:30:29Z codex · CURATED_RECORD — Added directly imaged triplet-base connectivity, two species examples, approximate Paramecium span, scoped EMDB provenance and inspected CC BY figure. Retained molecular identity, periodicity and mechanics as unresolved; no hypothesized protein membership or broad distribution asserted.

Source: data/structures/cytoskeleton/basal_body_triplet_base.yaml