LU domain
Protein domain
From Wikipedia, the free encyclopedia
The LU domain (Ly-6 antigen/uPAR) is an evolutionarily conserved protein domain of the three-finger protein superfamily. This domain is found in the extracellular domains of cell-surface receptors and in either GPI-anchored or secreted globular proteins, for example the Ly-6 family, CD59, and Sgp-2.[2][3]
A variety of GPI-linked cell-surface glycoproteins are composed of one or more copies of a conserved LU domain of about 100 amino-acid residues.[4][5] Among these proteins, most contain only a single LU domain, though small numbers of exceptions are known; well-studied family member uPAR has three tandem LU domains.[3]
Structure
This domain folds into five antiparallel beta sheets, a structure common to the three-finger protein family. The domain typically contains ten well-conserved cysteine residues involved in five disulfide bonds, though some examples such as two of the three uPAR domains have fewer.[3]
Examples
Besides uPAR, other receptors with LU domains include members of the transforming growth factor beta receptor (TGF-beta) superfamily, such as the activin type 2 receptor;[6] and bone morphogenetic protein receptor, type IA.[7] Other LU domain proteins are small globular proteins such as CD59 antigen, LYNX1, SLURP1, and SLURP2.[2][8]
Subfamilies
- Urokinase plasminogen activator surface receptor InterPro: IPR003631
- Cell-surface glycoprotein Ly-6/CD59 InterPro: IPR003632
Human proteins containing this domain
ARS; CD177; CD59; LY6D; LY6E; LY6H; LYNX1; LYPD2; LYPD3; LYPD4; LYPD5; LYPD6; PLAUR; PSCA; SLURP2; SLURP1; SPACA4; TEX101;
Functions
Many LU domain containing proteins are involved in cholinergic signaling and bind acetylcholine receptors, notably linking their function to a common mechanism of 3FTx toxicity.[2][3][9] Members of the Ly6/uPAR family are believed to be the evolutionary ancestors of the three-finger toxin (3FTx).[10] Other LU proteins, such as the CD59 antigen, have well-studied functions in regulation of the immune system.[9]