Important for the biogenesis of eisosomes, large cytoplasmic protein assemblies that localize to specialized domains on the plasma membrane to cluster specific proteins at sites of membrane invaginations. Required for efficient incorporation of the eisosome component PIL1 into eisosomes. Component of eisosomes, large cytoplasmic protein assemblies that localize to specialized domains termed MCCs on the plasma membrane. Localizes to eisosomes. Belongs to the SEG1 family.