SIN/MEN two-component GAP complex

GO:1990334 · Cytoskeleton · Multiprotein complex · Proposed

A protein complex that acts as a two-component GTPase-activating protein for the Tem1/Spg1 GTPase, thus regulating a signal transduction cascade (the mitotic exit network, MEN, in budding yeast; the septation initiation network, SIN, in fission yeast), which is required for mitotic exit and cytokinesis. The complex keeps the GTPase inactive until the spindle is properly oriented, thus inhibiting MEN/SIN activation. [GO:1990334]

Synonyms: Bfa1-Bub2 complex; Byr4-Cdc16 GAP complex

Part of: spindle pole body (GO:0005816)

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

Taxonomic distribution

• NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding yeast is the model system for the Bfa1-Bub2 branch of this two-component MEN GAP; no broader fungal distribution is asserted here. [DOI:10.1083/jcb.200507162]

Canonical examples

• NCBITaxon:4932 Saccharomyces cerevisiae — Reference budding-yeast system for the Bfa1-Bub2 GAP complex that restrains Tem1 to inhibit mitotic exit. [DOI:10.1083/jcb.200507162]

Functions

• MEN Tem1 GAP checkpoint inhibition — The budding-yeast Bfa1-Bub2 two-component GAP complex keeps Tem1 inactive at spindle pole bodies until spindle orientation permits MEN activation and mitotic exit.
  • GO:1990334 GO:1990334 defines the complex by two-component GTPase-activating activity toward Tem1/Spg1 and MEN/SIN inhibition.
  • DOI:10.1083/jcb.200507162 Fraschini et al. 2006 studied Bfa1-dependent Bub2 regulation of Tem1 and mitotic exit from spindle pole bodies in budding yeast.

Discussions

• INTERPRETATION (RESOLVED): Keep the SIN/MEN two-component GAP complex distinct from the broad SIN/MEN signaling complex and from SPB-localized SIN activation states. GO:1990334 denotes the narrower two-component GAP that inhibits Tem1/Spg1 GTPase signaling and is part of the spindle pole body. It is not equivalent to the broader GO:0160065 SIN/MEN signaling complex, nor to the GO:0160066 old-SPB interphase or GO:0160067 new-SPB anaphase SIN states.
• CURATION_TODO (OPEN): Resolve exact source-neutral family groundings for Bfa1/Bub2 and Byr4/Cdc16 GAP constituents. This first GO-backed record captures the two-component GAP complex without guessing InterPro, Pfam, NCBIfam, UniProtKB, or Complex Portal groundings for lineage-specific protein names.

Evidence

• GO:1990334 Gene Ontology cellular-component term for the SIN/MEN two-component GAP complex, with budding- and fission-yeast complex names as narrow synonyms.
• GO:1902773 Gene Ontology parent term for GTPase activator complex.
• GO:0005816 Gene Ontology cellular-component term for the spindle pole body, which contains the SIN/MEN two-component GAP complex by parthood.
• DOI:10.1083/jcb.200507162 Fraschini et al. 2006 studied localization and Tem1/MEN checkpoint function of the budding-yeast Bub2-Bfa1 complex at duplicated spindle pole bodies.

Curation history

• 2026-09-29T20:41:46Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
• 2026-09-29T20:42:48Z codex · EXPANDED_RECORD — Added GO narrow synonyms, GTPase-activator parentage, spindle-pole-body parthood, budding-yeast scope, a MEN Tem1 inhibition function, GO and literature evidence, and boundary/component discussions.

Source: data/structures/cytoskeleton/sin_men_two_component_gap_complex.yaml