This entry represents a group of SUN domain-containing proteins, including Suco (SUN domain-containing ossification factor) from animals and Slp1 from yeasts. SUN-domain containing proteins contain three structural features: a transmembrane, a coiled-coil, and a SUN domain.Suco regulates type I collagen synthesis in osteoblasts during their postnatal maturation []. Slp1 is required for localization of MPS3 (a SUN domain-containing protein) to the nuclear envelope [].