SUN domain (IPR012919)
Short name: SUN_dom
Overlapping homologous superfamilies
- Galactose-binding-like domain superfamily (IPR008979)
Sad1/UNC-84 (SUN)-domain proteins are inner nuclear membrane (INM) proteins that are part of bridging complexes linking cytoskeletal elements with the nucleoskeleton. Originaly identified based on an ~150-amino acid region of homology between the C terminus of the Schizosaccharomyces pombe Sad1 protein and the Caenorhabditis elegans UNC-84 protein, SUN proteins are present in the proteomes of most eucaryotes. In addition to the SUN domain, these proteins contain a transmembrane sequence and at least one coiled-coil domain and localise to the inner nuclear envelope. SUN proteins are anchored in the inner nuclear envelope by their transmembrane segment and oriented in the membrane such that the C-terminal SUN domain is located in the space between the inner and outer nuclear membrane. Here, the SUN domain can interact with the C- terminal tail of an outer nuclear envelope protein that binds to the cytoskeleton, including the centrosome [PMID: 15611647, PMID: 16923827, PMID: 19807882].
Some proteins known to contain a SUN domain are listed below:
- Fission yeast spindle pole body-associated protein Sad1.
- Yeast spindle pole body assembly component MPS3, essential for nuclear division and fusion.
- Yeast uncharacterised protein SLP1.
- Caenorhabditis nuclear migration and anchoring protein UNC-84.
- Caenorhabditis SUN domain-containing protein 1 (sun-1), involved in centrosome attachment to the nucleus.
- Mammalian sperm-associated antigen 4 protein (SPAG4), may assist the organisation and assembly of outer dense fibres (ODFs), a specific structure of the sperm tail.
- Mammalian sperm-associated antigen 4-like protein (SPAG4L).
- Mammalian SUN1.
- Mammalian SUN2.
- Mammalian SUN3.