Armadillo repeat

{{Pfam_box

| Symbol = Arm

| Name = Armadillo repeat domain

| image = PDB 3bct EBI.jpg

| width =

| caption = Structure of the armadillo domain of β-catenin.{{cite journal |vauthors=Huber AH, Nelson WJ, Weis WI |title=Three-dimensional structure of the armadillo repeat region of β-catenin |journal=Cell |volume=90 |issue=5 |pages=871–82 |date=September 1997 |pmid=9298899 |doi= 10.1016/S0092-8674(00)80352-9|s2cid=18612343 |doi-access=free }}

| Pfam = PF00514

| Pfam_clan = CL0020

| InterPro = IPR000225

| SMART = SM00185

| PROSITE = PS50176

| SCOP = 3bct

| TCDB =

| OPM family =

| OPM protein =

| CDD = cd00020

| PDB =

|Membranome superfamily = 350

}}

An armadillo repeat is a characteristic, repetitive amino acid sequence of about 42 residues in length that is found in many proteins. Proteins that contain armadillo repeats typically contain several tandemly repeated copies.{{cite journal | vauthors = Peifer M, Berg S, Reynolds AB | title = A repeating amino acid motif shared by proteins with diverse cellular roles | journal = Cell | volume = 76 | issue = 5 | pages = 789–91 | year = 1994 | pmid = 7907279 | doi = 10.1016/0092-8674(94)90353-0 | s2cid = 26528190 }}{{cite journal | vauthors = Groves MR, Barford D | title = Topological characteristics of helical repeat proteins | journal = Current Opinion in Structural Biology | volume = 9 | issue = 3 | pages = 383–9 | year = 1999 | pmid = 10361086 | doi = 10.1016/S0959-440X(99)80052-9 }} Each armadillo repeat is composed of a pair of alpha helices that form a hairpin structure. Multiple copies of the repeat form what is known as an alpha solenoid structure.

Examples of proteins that contain armadillo repeats include β-catenin, Sarm1 (SARM1),{{Cite web |title=Scopus preview - Scopus - Welcome to Scopus |url=https://www.scopus.com/home.uri |access-date=2023-03-21 |website=www.scopus.com}} α-importin,{{cite journal | vauthors = Herold A, Truant R, Wiegand H, Cullen BR | title = Determination of the functional domain organization of the importin alpha nuclear import factor | journal = J. Cell Biol. | volume = 143 | issue = 2 | pages = 309–18 | date = October 1998 | pmid = 9786944 | pmc = 2132842 | doi = 10.1083/jcb.143.2.309 }} plakoglobin,{{cite journal | vauthors = McCrea PD, Turck CW, Gumbiner B | title = A homolog of the armadillo protein in Drosophila (plakoglobin) associated with E-cadherin | journal = Science | volume = 254 | issue = 5036 | pages = 1359–61 | date = November 1991 | pmid = 1962194 | doi = 10.1126/science.1962194 | bibcode = 1991Sci...254.1359M }} adenomatous polyposis coli (APC),{{cite journal | vauthors = Hirschl D, Bayer P, Müller O | title = Secondary structure of an armadillo single repeat from the APC protein | journal = FEBS Lett. | volume = 383 | issue = 1–2 | pages = 31–6 | date = March 1996 | pmid = 8612785 | doi = 10.1016/0014-5793(96)00215-3 | s2cid = 36190869 | doi-access = }} and many others.

The term armadillo derives from the historical name of the β-catenin gene in the fruitfly Drosophila, where the armadillo repeat was first discovered. Although β-catenin was previously believed to be a protein involved in linking cadherin cell adhesion proteins to the cytoskeleton, recent work indicates that β-catenin regulates the homodimerization of alpha-catenin, which in turn controls actin branching and bundling.Nusse, Roel, and Hans Clevers. “Wnt/β-Catenin Signaling, Disease, and Emerging Therapeutic Modalities.” Cell, vol. 169, no. 6, 1 June 2017, pp. 985–999., doi:10.1016/j.cell.2017.05.016.

But, the armadillo repeat is found in a wide range of proteins with other functions. This type of protein domain is important in transducing WNT signals during embryonic development.