Conserved Site

CD59 antigen, conserved site (IPR018363)

Short name: CD59_antigen_CS


CD59 (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 signalling 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 polymerisation 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 haemoglobinuria (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 [PMID: 1850423], [PMID: 8394346]. 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 disulphide bonds - in U-PAR, the first copy of the domain lacks the fourth disulphide bond.

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

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

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE patterns