View source for Armadillo repeat

{{Pfam_box
| Symbol = Arm
| Name = Armadillo repeat domain
| image = PDB 3bct EBI.jpg
| width = 
| caption = Structure of the armadillo domain of [[beta catenin|β-catenin]].<ref name="pmid9298899">{{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 }}</ref>
| 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]] [[peptide sequence|sequence]] of about 42 [[residue (chemistry)#biochemistry|residues]] in length that is found in many proteins. Proteins that contain armadillo repeats typically contain several [[Protein tandem repeats|tandemly repeated]] copies.<ref name=pmid7907279>{{cite journal | vauthors = [[Mark Peifer|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 }}</ref><ref name=pmid10361086>{{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 }}</ref> 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 [[beta catenin|β-catenin]], Sarm1 ([[SARM1]]),<ref>{{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}}</ref> [[importin α|α-importin]],<ref name="pmid9786944">{{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 }}</ref> [[plakoglobin]],<ref name="pmid1962194">{{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 }}</ref> [[adenomatous polyposis coli]] (APC),<ref name="pmid8612785">{{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 =  }}</ref> and many others.

The term armadillo derives from the historical name of the [[β-catenin]] gene in the fruitfly ''[[Drosophila melanogaster|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.<ref>Nusse, Roel, and Hans Clevers. “Wnt/Î²-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.
</ref> 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 [[Embryogenesis|embryonic development]].

== Structure ==

The 3-dimensional fold of an armadillo repeat was first observed in the crystal structure of [[beta catenin|β-catenin]], where the 12 [[Protein tandem repeats|tandem repeats]] form a superhelix of [[alpha helices]] with three helices per unit.<ref name="pmid9298899"/> The cylindrical structure features a positively charged groove, which presumably interacts with the acidic surfaces of the known interaction partners of [[beta catenin|β-catenin]].<ref name="urlArmadillo (IPR000225)">{{cite web | url = https://www.ebi.ac.uk/interpro/entry/IPR000225 | title = Armadillo (IPR000225) | work = InterPro | publisher = EMBL-EBI }}</ref>

== References==
{{reflist}}

== External links ==
* {{ELM|TRG_NLS_Bipartite_1}}
* {{ELM|TRG_NLS_MonoCore_2}}
* {{ELM|TRG_NLS_MonoExtC_3}}
* {{ELM|TRG_NLS_MonoExtN_4}}
* {{MeshName|Armadillo+Domain+Proteins}}
* [http://www.expasy.org/cgi-bin/nicedoc.pl?PDOC50176 Armadillo/plakoglobin ARM repeat]{{Dead link|date=September 2023 |bot=InternetArchiveBot |fix-attempted=yes }} in [[PROSITE]]

{{Protein tandem repeats}}

[[Category:Armadillo repeat| ]]


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