1,3-beta-D-glucan synthase complex

GO:0000148 · Other · Multiprotein complex · Proposed

A protein complex that catalyzes the transfer of a glucose group from UDP-glucose to a (1->3)-beta-D-glucan chain. [GO:0000148]

Synonyms: 1,3-beta-glucan synthase complex; (1->3)-beta-glucan synthase complex

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

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
Fks catalytic subunits	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	FKS1, FKS2		UNKNOWN	Integral membrane catalytic subunits of the budding-yeast 1,3-beta-D-glucan synthase enzyme complex. `DOI:10.1073/pnas.91.26.12907` Douglas et al. 1994 showed that Saccharomyces cerevisiae FKS1 encodes an integral membrane protein subunit of 1,3-beta-D-glucan synthase. `DOI:10.1128/MCB.15.10.5671` Mazur et al. 1995 characterized differential function of the homologous yeast Fks1p and Fks2p glucan-synthase subunits.
Rho1 GTPase regulatory subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	RHO1		UNKNOWN	Regulatory GTPase subunit that stimulates the Fks-containing 1,3-beta-D-glucan synthase complex. `DOI:10.1126/science.272.5259.279` Qadota et al. 1996 identified yeast Rho1p as a regulatory subunit of 1,3-beta-glucan synthase and showed its in vivo association with Fks1p. `DOI:10.1074/jbc.271.24.14604` Mazur and Baginsky 1996 found that yeast 1,3-beta-D-glucan synthase activity requires Rho1p.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Qadota et al. identified Rho1p as a regulatory subunit and connected it with Fks1p in the budding-yeast 1,3-beta-D-glucan synthase complex; broader fungal distribution was left unasserted in this first record. [DOI:10.1126/science.272.5259.279]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast model in which Rho1p was identified as a regulatory GTPase that associates with Fks1p in the 1,3-beta-D-glucan synthase complex. [DOI:10.1126/science.272.5259.279]

Functions

1,3-beta-D-glucan synthase activity GO:0003843 — The complex transfers glucose from UDP-glucose to extend a (1->3)-beta-D-glucan chain.
- GO:0003843 Gene Ontology molecular-function term for 1,3-beta-D-glucan synthase activity.
- PMID:7983071 Mol et al. 1994 assayed yeast 1,3-beta-glucan synthase regulation by a GTP-binding protein.
fungal-type cell wall (1->3)-beta-D-glucan biosynthetic process GO:0071970 — The enzyme complex synthesizes 1,3-beta-D-glucan for the fungal cell wall.
- GO:0071970 Gene Ontology biological-process term for fungal-type cell wall 1,3-beta-D-glucan biosynthetic process.
- DOI:10.1073/pnas.91.26.12907 Douglas et al. 1994 connected FKS1 with the membrane-bound 1,3-beta-D-glucan synthase that builds a major yeast cell-wall glucan.

Mechanism graphs

Rho1 stimulates Fks-dependent 1,3-beta-glucan synthesis (FUNCTION)

In budding yeast, Fks membrane proteins provide the catalytic subunits of 1,3-beta-D-glucan synthase, while Rho1p associates with Fks1p and activates glucan-synthase activity.

Subject	Predicate	Object	Evidence
Fks catalytic subunits	is catalytic constituent of	1,3-beta-D-glucan synthase complex	`DOI:10.1073/pnas.91.26.12907` Douglas et al. 1994 identified Fks1p as an integral membrane subunit of 1,3-beta-D-glucan synthase. `DOI:10.1128/MCB.15.10.5671` Mazur et al. 1995 characterized Fks1p and Fks2p as homologous yeast glucan-synthase subunits.
Rho1 GTPase regulatory subunit	is regulatory constituent of	1,3-beta-D-glucan synthase complex	`DOI:10.1126/science.272.5259.279` Qadota et al. 1996 identified Rho1p as a regulatory subunit and found in vivo association with Fks1p.
Rho1 GTPase regulatory subunit	stimulates	1,3-beta-D-glucan synthase activity	`DOI:10.1074/jbc.271.24.14604` Mazur and Baginsky 1996 found that Rho1p is required for 1,3-beta-D-glucan synthase activity. `PMID:7983071` Mol et al. 1994 connected a GTP-binding protein to regulation of yeast 1,3-beta-glucan synthase.
1,3-beta-D-glucan synthase complex	synthesizes	1,3-beta-D-glucan	`GO:0000148` GO:0000148 defines the complex by 1,3-beta-D-glucan synthase catalysis. `GO:0003843` GO:0003843 describes the molecular function as extension of a (1->3)-beta-D-glucan chain.
1,3-beta-D-glucan	is synthesized for	fungal-type cell wall	`GO:0071970` GO:0071970 covers formation of 1,3-beta-D-glucans in fungal cell walls.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings for the Saccharomyces Fks1/Fks2 catalytic pair and the Rho1 regulatory subunit. The initial record follows experimentally named Saccharomyces proteins and avoids guessing InterPro, Pfam, NCBIfam, or UniProtKB accessions that would broaden component identities beyond the curated Fks1/Fks2 and Rho1 boundary.
CURATION_TODO (RESOLVED): Should upstream Rho1 regulators and cell-integrity pathway proteins be curated as components of the synthase complex? Rho1 is curated because it was identified as a regulatory subunit of 1,3-beta-glucan synthase. Upstream Rho1 regulators and wall-stress signaling proteins act on or through Rho1 outside the defined Fks/Rho1 enzyme complex.

Evidence

GO:0000148 Gene Ontology cellular-component term for the 1,3-beta-D-glucan synthase complex.
GO:0003843 Gene Ontology molecular-function term for 1,3-beta-D-glucan synthase activity.
GO:0071970 Gene Ontology biological-process term for fungal-type cell wall 1,3-beta-D-glucan biosynthesis.
PMID:7983071 Mol et al. 1994, 'A GTP-binding protein regulates the activity of (1-->3)-beta-glucan synthase, an enzyme directly involved in yeast cell wall morphogenesis', Journal of Biological Chemistry.
DOI:10.1073/pnas.91.26.12907 Douglas et al. 1994, 'The Saccharomyces cerevisiae FKS1 (ETG1) gene encodes an integral membrane protein which is a subunit of 1,3-beta-D-glucan synthase', Proceedings of the National Academy of Sciences.
DOI:10.1128/MCB.15.10.5671 Mazur et al. 1995, 'Differential expression and function of two homologous subunits of yeast 1,3-beta-D-glucan synthase', Molecular and Cellular Biology.
DOI:10.1126/science.272.5259.279 Qadota et al. 1996, 'Identification of yeast Rho1p GTPase as a regulatory subunit of 1,3-beta-glucan synthase', Science.
DOI:10.1074/jbc.271.24.14604 Mazur and Baginsky 1996, 'Activity of 1,3-beta-D-Glucan Synthase Requires the GTP-binding Protein Rho1', Journal of Biological Chemistry.

Curation history

2026-09-18T23:51:04Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-18T23:52:27Z codex · EXPANDED_RECORD — Added GO synonymy, Fks catalytic and Rho1 regulatory components, Saccharomyces cerevisiae scope, GO-grounded glucan-synthase functions, DOI/PMID evidence, a Rho1/Fks function graph, and component-grounding and upstream-regulator boundary discussions.
2026-09-18T23:56:41Z codex · FIXED_GO_LABEL — Updated the GO:0071970 function label to the canonical Gene Ontology label used by the id-label correspondence audit.
2026-09-19T00:05:21Z codex · ADDRESSED_REVIEW — Addressed PR #1206 review issues #1207, #1208, and #1209 by narrowing the row-level Saccharomyces notes to their Qadota Fks1/Rho1 citation, constraining Fks/Rho1 grounding language to the curated Saccharomyces boundary, and correcting the Mazur and Baginsky JBC title.

Source: data/structures/other/1_3_beta_d_glucan_synthase_complex.yaml