ITGA11 (integrin, alpha 11)

	Scematic structure of the I-domain containing α11 integrin. A. The integrin's α subunit primary structure, including predicted divalent cation-binding sites (Mg2 as red star, and Ca2 as gray stars) is shown. The position of the inserted sequence of 22 amino acids in the Calf-1 domain is marked. B. Schematic representations of straightened (active) conformations of the integrin. The arrangement of domains is based on the 3-dimensional crystal structure of the αvβ3-integrin, with an I domain added between the second and third β-propeller repeats. I-d indicates I domain; PSI, plexin/semaphorin/integrin; and TM, -tail domain of integrin β subunit.
Description	The mature α11 peptide is 1166-amino acid-long (M.W. 145 kDa in SDS-PAGE under non-reducing conditions), which is longer than any other currently identified integrin α-chain (with the closest being αE, which is composed of 1160 amino acids). The extracellular domain contains seven FG-GAP repeats in the amino-terminal end with an inserted I domain between repeats 2 and 3. The I domain consists of 195 amino acids and includes a conserved metal ion-dependent adhesion site motif. In addition to the metal chelating site in the I domain, three potential divalent cation binding motifs with the consensus sequence DXD/NXDXXXD are present in repeats 5-7. A total of 20 cysteines are located in the extracellular domain. Of these, 16 are conserved in the most closely related integrin α10- and α1-chains, and they may contribute to intramolecular disulfide bonds. There is an inserted 22 amino acid sequence in the calf-1 domain in the stalk region at amino acids 804-826, distinguishing α11 from other integrin α-chains. The transmembrane region (amino acids 1142-1164) is 23 amino acids long and is followed by a cytoplasmic tail of 24 amino acids. The cytoplasmic tail contains the sequence GFFRS instead of the conserved GFFKR sequence found in all other alpha-chains except ITGA8 - alpha 10.
Expression	Analysis of α11 protein and mRNA expression and distribution in human and mouse embryos revealed a restricted expression on mesenchymal non-muscle cells in areas of highly organized interstitial collagen networks.
Localisation	Membrane-bound
Function	Integrin α11 subunit binds integrin beta 1 subunit to form a heterodimer and function as a receptor for interstitial collagens (with highest affinity for collagen type I). It is involved in cell attachment, cell migration and collagen reorganization on mesenchymal non-muscle cells.
Homology	When compared with other I domain-containing collagen-binding integrin subunits, α11 amino acid sequence shows the highest overall identity with integrin alpha 10 (42% identity) followed by integrin alpha 1 (37% identity), and integrin alpha 2 (35% identity). Of the non-I domain-containing integrins, integrin alpha 4 and integrin alpha 9 show the highest sequence similarity to α11. ITGA11 shows 86% identity with mouse integrin α11 at the nucleotide level, translating to 89% identity at the amino-acid level.

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