SUN domain

{{Infobox protein family

| Symbol = Sad1_UNC

| Name = Sad1_UNC

| image =

| width =

| caption =

| Pfam = PF07738

| Pfam_clan = CL0202

| InterPro = IPR012919

| SMART =

| PROSITE =

| MEROPS =

| SCOP =

| TCDB =

| OPM family =

| OPM protein =

| CAZy =

| CDD =

}}

SUN (Sad1p, UNC-84) domains are conserved C-terminal protein regions a few hundred amino acids long. SUN domains are usually found following a transmembrane domain and a less conserved region of amino acids. Most proteins containing SUN domains are thought to be involved in the positioning of the nucleus in the cell. It is thought that SUN domains interact directly with KASH domains in the space between the outer and inner nuclear membranes to bridge the nuclear envelope and transfer force from the nucleoskeleton to the cytoplasmic cytoskeleton which enables mechanosensory roles in cells.{{cite journal | vauthors = Uzer G, Thompson WR, Sen B, Xie Z, Yen SS, Miller S, Bas G, Styner M, Rubin CT, Judex S, Burridge K, Rubin J | title = Cell Mechanosensitivity to Extremely Low-Magnitude Signals Is Enabled by a LINCed Nucleus | journal = Stem Cells | volume = 33 | issue = 6 | pages = 2063–76 | date = June 2015 | pmid = 25787126 | pmc = 4458857 | doi = 10.1002/stem.2004 }} SUN proteins are thought to localize to the inner nuclear membrane.{{cite journal | vauthors = Tzur YB, Wilson KL, Gruenbaum Y | title = SUN-domain proteins: 'Velcro' that links the nucleoskeleton to the cytoskeleton | journal = Nature Reviews. Molecular Cell Biology | volume = 7 | issue = 10 | pages = 782–8 | date = October 2006 | pmid = 16926857 | doi = 10.1038/nrm2003 | s2cid = 19519227 | url = https://zenodo.org/record/999029 }} The S. pombe Sad1 protein localises at the spindle pole body. In mammals, the SUN domain is present in two proteins, Sun1 and Sun2. The SUN domain of Sun2 has been demonstrated to be in the periplasm.{{cite journal | vauthors = Hodzic DM, Yeater DB, Bengtsson L, Otto H, Stahl PD | title = Sun2 is a novel mammalian inner nuclear membrane protein | journal = The Journal of Biological Chemistry | volume = 279 | issue = 24 | pages = 25805–12 | date = June 2004 | pmid = 15082709 | doi = 10.1074/jbc.M313157200 | doi-access = free }}{{cite journal | vauthors = Raff JW | title = The missing (L) UNC? | journal = Current Biology | volume = 9 | issue = 18 | pages = R708-10 | date = September 1999 | pmid = 10508607 | doi = 10.1016/S0960-9822(99)80446-1 | s2cid = 14827859 | doi-access = free }}