bgs4 (O74475, SPCC1840.02c; cwg1, orb11, pbr1) notes

Summary

Essential GT48/FKS 1,3-beta-glucan synthase; the only Bgs subunit shown to be part of the GS enzyme PMID:15615781.
Makes the major branched beta-1,3-glucan of the wall and most GS activity [PMID:34959732 "It synthesizes the branched β(1,3)-D-glucan and is responsible for most GS activity"; PMID:24165938 "Bgs4 is responsible for the cell wall B-BG synthesis and the major β(1,3)GS activity."].
Septum: arrives after septum initiation; required for the secondary septum and primary septum completion PMID:24165938.
Ring coupling: PMID:24165938.
Trafficking: poles -> late Golgi -> PM next to the ring, needs Rga7 PMID:25977474.
Regulation: Rho1 regulatory subunit PMID:35049972; Rgf1 GEF PMID:23907979.
Not a Ghs2 partner [PMID:42786154 "whereas GFP-Ghs2 and RFP-Bgs4 did not"; "In contrast, GFP-Ghs2 localization was unaffected in bgs4 (cwg1-1) and bgs1 (cps1-191) mutants"]. Associates with Smi1 (stated in PMID:42786154).
Drug target: pbr1 resistance alleles are bgs4 point mutations PMID:34959732.

GO:0140752 (TAS) accepted as core MF; all GO:0003843 rows MODIFY -> GO:0140752 (coordinator guidance; PomBase GO-CAM gomodel:6918f23700003787 uses GO:0140752 for Bgs4 in secondary cell septum biogenesis). Caveat: branching rests on mutant wall composition, not on a reconstituted enzyme; for Bgs3 branching is attributed to Ghs2.
General process rows (GO:0006075, GO:0051278) MODIFY -> GO:0071970; membrane -> plasma membrane; cell septum -> division septum; contractile ring -> cleavage furrow; cell cortex of growing tip -> plasma membrane of cell tip (Bgs4 is integral PM, not cortical).
Golgi (transit), spore wall, mating projection tip, new growing tip, primary septum kept as non-core; cytoplasm HDA marked over-annotated.