flagellum attachment zone

GO:0120119 · Cytoskeleton · Other · Proposed

A network of cytoskeletal and membranous connections responsible for the lateral attachment of the cilium to the cell body in some trypanosomatid species. [GO:0120119]

Synonyms: FAZ

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

Components

Component	Type	Part of / acts on	Grounding	Genes	Essential	Role
FAZ filament	Other	part of	Reviewed label only (reviewed name; no accession asserted)			Cytoskeletal filament-domain core of the trypanosome FAZ that runs along the attached flagellum and contains FAZ1, FAZ2, CC2D and additional FAZ proteins. `DOI:10.1016/j.pt.2015.12.010` Sunter and Gull 2016 reviewed the FAZ filament as one of the FAZ domains and tabulated FAZ1, FAZ2 and CC2D as filament-domain proteins. `DOI:10.1242/jcs.168377` Zhou et al. 2015 localized newly identified FAZ proteins to the FAZ filament and assayed FAZ filament assembly and maintenance after RNAi.
FAZ1 repetitive filament protein	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	FAZ1, Tb927.4.3740	UNKNOWN	Large repetitive protein that marks the FAZ filament and is required for normal FAZ filament structure and function. `DOI:10.1016/j.protis.2007.08.005` Vaughan et al. 2008 identified FAZ1 as a repetitive T. brucei FAZ filament protein and tested its requirement for FAZ filament structure and function. In procyclic T. brucei, FAZ1 RNAi left aberrant FAZ-like structures and other filament markers despite attachment and cytokinesis defects. Because knockdown does not establish complete protein absence, these results leave assembly essentiality UNKNOWN; they support a requirement for normal filament organization, not an absolute block of FAZ formation. `DOI:10.1016/j.pt.2015.12.010` Sunter and Gull 2016 list Tb927.4.3740/FAZ1 in the FAZ filament domain in their FAZ protein summary.
FAZ2 filament protein	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	FAZ2, Tb927.1.4310	UNKNOWN	FAZ filament protein needed to maintain the FAZ filament and the stability of multiple FAZ filament components. `DOI:10.1242/jcs.168377` Zhou et al. 2015 identified FAZ2 by localization screening and found that FAZ2 knockdown disrupted the FAZ filament and destabilized other FAZ filament proteins. `DOI:10.1016/j.pt.2015.12.010` Sunter and Gull 2016 list Tb927.1.4310/FAZ2 in the FAZ filament domain.
CC2D FAZ filament protein	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	CC2D, Tb927.4.2080	UNKNOWN	Coiled-coil and C2-domain FAZ filament protein that contributes to FAZ assembly and complexes with FAZ2. `DOI:10.1242/jcs.087676` Zhou et al. 2011 characterized a coiled-coil and C2-domain protein required for FAZ assembly and T. brucei cell morphology. `DOI:10.1242/jcs.168377` Zhou et al. 2015 identified CC2D as a FAZ2 partner through affinity purification.

Taxonomic distribution

NCBITaxon:5691 Trypanosoma brucei — COMMON: The FAZ runs alongside the attached flagellum in procyclic and bloodstream T. brucei forms and has been dissected by RNAi, tagging and microscopy. [DOI:10.1016/j.pt.2015.12.010]

Canonical examples

NCBITaxon:5691 Trypanosoma brucei — Trypanosome model in which a localization-based screen identified FAZ2 on the FAZ filament, and FAZ2 knockdown connected a FAZ filament constituent to filament maintenance and cytokinesis. [DOI:10.1242/jcs.168377]

Functions

lateral flagellum-cell-body attachment — The FAZ links the motile cilium to the trypanosome cell body along the lateral flagellum attachment path.
- DOI:10.1111/j.1550-7408.1999.tb04592.x Kohl et al. 1999 followed assembly of the flagellum attachment zone complex during the T. brucei cell cycle.
- DOI:10.1016/j.pt.2015.12.010 Sunter and Gull 2016 reviewed the FAZ as the structure that mediates lateral attachment of the T. brucei flagellum to the cell body.
trypanosome cell morphogenesis — FAZ assembly and length help regulate trypanosome cell shape, cell length and positions of single-copy organelles.
- DOI:10.1016/j.pt.2015.12.010 Sunter and Gull 2016 reviewed FAZ length and composition as regulators of trypanosome morphology and organelle positioning.
flagellum attachment zone organization — New FAZ proteins are incorporated near the proximal base of the FAZ filament as the trypanosome builds a daughter FAZ.
- DOI:10.1242/jcs.168377 Zhou et al. 2015 found proximal incorporation of FAZ filament proteins during FAZ filament assembly.

Mechanism graphs

FAZ filament proteins maintain lateral flagellum attachment (FUNCTION)

FAZ1, FAZ2 and CC2D are curated T. brucei FAZ filament constituents that contribute to the FAZ cytoskeletal filament; the larger FAZ network mediates lateral flagellum attachment and helps set trypanosome morphology.

Subject	Predicate	Object	Evidence
FAZ1	contributes to	FAZ filament	`DOI:10.1016/j.protis.2007.08.005` Vaughan et al. 2008 linked FAZ1 depletion to defects in FAZ filament structure and function.
FAZ2	stabilizes	FAZ filament	`DOI:10.1242/jcs.168377` Zhou et al. 2015 showed that FAZ2 knockdown disrupted the FAZ filament and destabilized multiple FAZ filament proteins.
CC2D	interacts with	FAZ2	`DOI:10.1242/jcs.168377` Zhou et al. 2015 identified CC2D as a FAZ2 partner by affinity purification.
FAZ filament	forms domain of	flagellum attachment zone	`DOI:10.1016/j.pt.2015.12.010` Sunter and Gull 2016 describe the FAZ filament domain in their FAZ structural zone model.
flagellum attachment zone	mediates	lateral flagellum-cell-body attachment	`DOI:10.1016/j.pt.2015.12.010` Sunter and Gull 2016 review lateral flagellum attachment as the defining FAZ role.
lateral flagellum-cell-body attachment	supports	trypanosome cell morphogenesis	`DOI:10.1016/j.pt.2015.12.010` Sunter and Gull 2016 review the FAZ as a regulator of trypanosome morphology.

Discussions

CURATION_TODO (OPEN): Resolve membrane, flagellum-domain, microtubule-quartet and anterior-tip FAZ proteins before expanding this record beyond the FAZ filament-domain proteins curated here. The FAZ spans multiple membranes and cytoskeletal domains. This first record keeps the protein boundary to the FAZ filament-domain proteins FAZ1, FAZ2 and CC2D that were directly tied to filament assembly or integrity.

Evidence

DOI:10.1111/j.1550-7408.1999.tb04592.x Kohl, Sherwin and Gull 1999, Assembly of the paraflagellar rod and the flagellum attachment zone complex during the Trypanosoma brucei cell cycle, Journal of Eukaryotic Microbiology.
DOI:10.1016/j.protis.2007.08.005 Vaughan et al. 2008, A Repetitive Protein Essential for the Flagellum Attachment Zone Filament Structure and Function in Trypanosoma brucei, Protist.
DOI:10.1242/jcs.087676 Zhou et al. 2011, A coiled-coil- and C2-domain-containing protein is required for FAZ assembly and cell morphology in Trypanosoma brucei, Journal of Cell Science.
DOI:10.1242/jcs.168377 Zhou et al. 2015, Assembly and maintenance of the flagellum attachment zone filament in Trypanosoma brucei, Journal of Cell Science.
DOI:10.1016/j.pt.2015.12.010 Sunter and Gull 2016, The Flagellum Attachment Zone: The Cellular Ruler of Trypanosome Morphology, Trends in Parasitology.

Curation history

2026-09-12T02:02:35Z claude · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-12T02:03:34Z claude · EXPANDED_RECORD — Added FAZ synonymy, FAZ filament-domain components, Trypanosoma brucei taxonomic scope, lateral attachment and morphogenesis functions, a FAZ filament assembly graph, core literature evidence, and a TODO for nonfilament FAZ domains.
2026-09-12T02:10:02Z claude · ADDRESS_REVIEW — Resolved #565 by narrowing the T. brucei canonical example to the FAZ2 claims covered by Zhou et al. 2015; resolved #566 by changing the FAZ filament component type from PROTEIN_COMPLEX to OTHER.
2026-10-11T23:33:49Z codex · ADDRESS_SAVED_REVIEW — Addressed #2269: retained FAZ1 normal-structure function while leaving assembly essentiality UNKNOWN because RNAi retains abnormal FAZ structures and does not prove complete protein loss.

Source: data/structures/cytoskeleton/flagellum_attachment_zone.yaml