Homophilic binding protein that enables kin discrimination in heterogeneous yeast populations by mediating homotypic cell-cell interactions during flocculation, a reversible and asexual process in which cells adhere to form aggregates (flocs) (PubMed:32286952, PubMed:25960408, PubMed:27547826, PubMed:17921350, PubMed:22129043). Plays a role in cell-substrate adhesion, haploid invasive growth, diploid pseudohyphae formation and biofilm (flor) development (PubMed:18001350, PubMed:11027318, PubMed:11157168, PubMed:16043420, PubMed:17921350, PubMed:20619652, PubMed:8710886, PubMed:8955395). Adhesive activity is inhibited by mannose, but not by glucose, maltose, sucrose or galactose (PubMed:16043420, PubMed:22129043). The protein is attached to the cell wall via a GPI-anchor and is also shed liberally into extracellular fluid; increased shedding is associated with biofilm mat expansion but decreased invasive growth. The number of the intragenic tandem repeats varies between different S.cerevisiae strains. There is a linear correlation between protein size and the extend of adhesion: the more repeats, the stronger the adhesion properties and the greater the fraction of flocculating cells (By similarity). The Flo11 domain contains aromatic residues that form two hydrophobic bands on the surface of the protein that confer homophilic binding (PubMed:32286952, PubMed:25960408, PubMed:22129043). The hydrophobic bands are lined by stretches of acidic residues that may sensitise the protein to environmental pH (PubMed:25960408). The domain is required for biofilm formation (PubMed:25960408). The domain does not interact with mannose or calcium ions (PubMed:22129043, PubMed:25960408). Extensively O-mannosylated. The GPI-anchor is attached to the protein in the endoplasmic reticulum and serves to target the protein to the cell surface. There, the glucosamine-inositol phospholipid moiety is cleaved off and the GPI-modified mannoprotein is covalently attached via its lipidless GPI glycan remnant to the 1,6-beta-glucan of the outer cell wall layer (By similarity). A soluble form is probably produced by proteolytic cleavage at the cell surface (shedding). In the reference strain S288C, the transcriptional activator FLO8 contains an internal in-frame stop codon, leading to impaired FLO11 expression in this strain. Belongs to the flocculin family. Highly divergent.