T-cell surface glycoprotein CD5 (IPR003566)

Short name: Tcell_CD5

Overlapping homologous superfamilies


Family relationships



The egg peptide speract receptor is a transmembrane glycoprotein of about 500 amino acids [PMID: 2538832]. Topologically, it comprises a large extracellular domain of about 450 residues, followed by a transmembrane domain and a short cytoplasmic region of about 12 amino acids. The extracellular domain contains 4 repeats of a well-conserved region, which spans 115 amino acids and contains 6 conserved cysteines. A similar domain is also found towards the C terminus of macrophage scavenger receptor type I [PMID: 1978939], a membrane glycoprotein implicated in the pathologic deposition of cholesterol in arterial walls during artherogenesis, and in the CD5 glycoprotein, which acts as a receptor in regulating T-cell proliferation.

The T1/Leu-1/CD5 glycoprotein is expressed at the surface membrane of all mature T cells. It has been implicated both in the proliferative response of activated T cells and in T-cell helper function [PMID: 3093892]. The complete amino-acid sequence of the T1 precursor has been deduced from cDNA clones. The protein contains a classical signal peptide; a 347-residue extracellular segment; a transmembrane region; and a 93-residue intra- cellular segment [PMID: 3093892]. The extracellular region contains several cysteine residues and comprises 2 speract receptor domains separated by a proline/ threonine-rich region [PMID: 3093892]. CD5 has been shown to function as a receptor, delivering co-stimulatory signals to T-cells, interacting specifically with the cell-surface protein CD72 (Lyb-2 in mice) exclusive to B-cells [PMID: 1711157].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

No terms assigned in this category.

Cellular Component

GO:0016020 membrane

Contributing signatures

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