Septins are GTPases involved in cytokinesis that assemble early in the cell cycle as a patch at the incipient bud site and form a ring approximate 15 minutes before bud emergence, which transforms into an hour-glass shaped collar of cortical filaments that spans both sides of the mother-bud neck. This collar persists until just before cytokinesis, when it splits into two rings that occupy opposite sides of the neck. The septins at the bud neck serve as a structural scaffold that recruits different components involved in diverse processes at specific stages during the cell cycle. Many proteins bind asymmetrically to the septin collar. The septin assembly is regulated by protein kinases GIN4 and/or CLA4. May act by recruiting MYO1 and HOF1, a protein involved in septation, to the site of cleavage. Septins are also involved in cell morphogenesis, bud site selection, chitin deposition, cell cycle regulation, cell compartmentalization and spore wall formation. Component of the septin complex which consists of CDC3, CDC10, CDC11, CDC12 and probably SHS1 and rearranges to a cortical collar of highly ordered filaments at the mother-bud-neck. A complex formed by CDC3, CDC10, CDC11 and CDC12 is capable of forming long filaments in vitro and the components seem to be present in a 2:2:2:2 arrangement in vivo. The filaments are proposed to be formed by the end-to-end polymerization of CDC3-CDC12-CDC11 complexes with CDC10 serving as a bridge to bundle the polymers into paired filaments. Component of the GIN4 complex composed of at least BNI5, CDC3, CDC10, CDC11, CDC12, GIN4, NAP1 and SHS1. Self-associates. Interacts with SIZ1 and SYP1. Present at the bud neck during cell division. Probably interacts with phosphoinosides such as phosphatidylinositol 4-phosphate or phosphatidylinositol 5-phosphate. Phosphorylated by CDC28. Phosphorylation at the end of G1 may facilitate initiation of a new cell cycle by promoting disassembly of the obsolete septin ring from the previous cell cycle. Sumoylated during mitosis on the mother cell side of the bud neck by UBC9/SIZ1. Sumoylation probably plays a central role in regulating septin ring disassembly during the cell cycle. Belongs to the TRAFAC class TrmE-Era-EngA-EngB-Septin-like GTPase superfamily. Septin GTPase family.