CD59 antigen

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u-PAR/Ly-6 domain
Symbol UPAR_LY6
Pfam PF00021
InterPro IPR001526
SCOP 1erg
CDD cd00117

CD59 antigen (also called 1F-5Ag, H19, HRF20, MACIF, MIRL, P-18 or protectin) inhibits formation of membrane attack complex (MAC), thus protecting cells from complement-mediated lysis. It has a signaling role, as a GPI anchored molecule, in T cell activation and appears to have some role in cell adhesion through CD2 (controversial). CD59 associates with C9, inhibiting incorporation into C5b-8 preventing terminal steps in polymerization of the (MAC) in plasma membranes. Genetic defects in GPI-anchor attachment that cause a reduction or loss of both CD59 and CD55 on erythrocytes produce the symptoms of the disease paroxysmal nocturnal hemoglobinuria (PNH).

A variety of GPI-linked cell-surface glycoproteins are composed of one or more copies of a conserved domain of about 100 amino-acid residues.[2][3] Among these proteins, U-PAR contains three tandem copies of the domain, while all the others are made up of a single domain.

As shown in the following schematic, this conserved domain contains 10 cysteine residues involved in five disulfide bonds - in U-PAR, the first copy of the domain lacks the fourth disulfide bond.

    +------+     +------------------------+                    +---+
    |      |     |                        |                    |   |
 |                     |                       |              |
 +---------------------+                       +--------------+

'C': conserved cysteine involved in a disulfide bond.

CD molecules are leucocyte antigens on cell surfaces. CD antigens nomenclature is updated at Protein Reviews On The Web (


Human proteins containing this domain[edit]

ARS[disambiguation needed]; CD177; CD59; LY6D; LY6E; LY6H; LYNX1; LYPD2; LYPD3; LYPD4; LYPD5; LYPD6; PLAUR; PSCA; SLURP2; SLURP1; SPACA4; TEX101;


  1. ^ PDB 2J8B; Leath KJ, Johnson S, Roversi P, Hughes TR, Smith RA, Mackenzie L, Morgan BP, Lea SM (August 2007). "High-resolution structures of bacterially expressed soluble human CD59". Acta Crystallogr. Sect. F Struct. Biol. Cryst. Commun. 63 (Pt 8): 648–52. doi:10.1107/S1744309107033477. PMC 2335151. PMID 17671359. 
  2. ^ Patthy L, Blasi F, Behrendt N, Ploug M, Houen G, Dano K (1991). "The ligand-binding domain of the cell surface receptor for urokinase-type plasminogen activator". J. Biol. Chem. 266 (12): 7842–7847. PMID 1850423. 
  3. ^ Ploug M, Dano K, Kjalke M, Ronne E, Weidle U, Hoyer-Hansen G (1993). "Localization of the disulfide bonds in the NH2-terminal domain of the cellular receptor for human urokinase-type plasminogen activator. A domain structure belonging to a novel superfamily of glycolipid-anchored membrane proteins". J. Biol. Chem. 268 (23): 17539–17546. PMID 8394346. 

This article incorporates text from the public domain Pfam and InterPro IPR001526