Alternate catalytic subunit of the 1,3-beta-glucan synthase (GS). Synthesizes 1,3-beta-glucan, a major structural component of the yeast cell wall. Involved in cell wall synthesis, maintenance and cell wall remodeling. [(1->3)-beta-D-glucosyl](n) + UDP-alpha-D-glucose = [(1->3)-beta-D-glucosyl](n+1) + H(+) + UDP Component of the 1,3-beta-glucan synthase (GS), composed of two alternate catalytic subunits FKS1 or GSC2, and a regulatory subunit RHO1. Interacts with RHO1, which is a GTP-binding protein. Localizes to the sites of polarized growth. Colocalizes with cortical actin patches and moves on the cell surface at the sites of cell wall remodeling. Actin patch motility is required for the movement. Early at the cell cycle, localizes at the presumed bud site of the mother cell and at the tip of the small bud. As the bud enlarges, appears as discernible spots in the medium-sized bud and these spots colocalize with actin patches. Late in the cell cycle, disappears in large budded cells, while the actin patches disperse over the cell. During cytokinesis, is concentrated in the neck, overlapping with the location of cortical actin patches. During vegetative growth. Expressed periodically during the cell cycle. Cells are hypersensitive to immunosuppressant drugs FK506 and cyclosporin A (CsA) due to the inhibition of calcineurin phosphatase activity by the receptor-drug complexes and is dependent on calcineurin for vegetative growth. It confers a slow growth phenotype which is partially suppressed by exogenously added Ca(2+) and exacerbated by EGTA. Simultaneous disruption of CNA1 and CNA2 or CNB1 is lethal in FKS1-1. Disruption of FPR1 or CPR1 results in the loss of hypersensitivity. Overexpression of CNA1 or CNA2, in conjunction with CNB1, results in a significant decrease in hypersensitivity to FK506 and CsA. FKS1-8 mutant is sensitive to FK506 and cyclosporin A, has increased tendency to lyse and exhibits slow growth that is improved by the addition of osmotic stabilizing agents. It is more sensitive to the drugs when grown on galactose compared to dextrose. ETG1-1 mutant is resistant to the cell wall active echinocandins, which are inhibitors of 1,3-beta-D-glucan synthase. ETG1-4 mutant is hypersensitive to the chitin synthase inhibitor nikkomycin Z. Deletion of FKS1 leads to hypersensitivity to echinocandin-like antifungal lipopeptide caspofungin, a 1,3-beta-glucan synthase inhibitor. Deletion mutant also displays a 30% reduction in 1,3-beta-glucan and 15% reduction in alkali-insoluble 1,6-beta-glucan compared to wild-type. Increases cellular chitin level (PubMed:17142567). Increases chitin chain length (PubMed:17142567). Belongs to the glycosyltransferase 48 family.