PROSITE documentation PDOC00216

Integrins beta chain cysteine-rich domain signature

Integrins [1,2] are a large family of cell surface receptors that mediate cell to cell as well as cell to matrix adhesion. Some integrins recognize the R-G-D sequence in their extracellular matrix protein ligand. Structurally, integrins consist of a dimer of an α and a β chain. Each subunit has a large N-terminal extracellular domain followed by a transmembrane domain and a short C-terminal cytoplasmic region. Some receptors share a common β chain while having different α chains. The sequence of a number of different β chains has been determined and are listed below:

• Integrin β-1, which associates with α-1 to form a laminin receptor, with α-2 to form a collagen receptor, with α-4 to interact with VCAM-1, with α-5 to form a fibronectin receptor, and with α-8.
• Integrin β-2, which associates with α-L (LFA-1) to interact with ICAM-1, and with α-M (MAC-1) or α-X (p150,95) to form the receptor for the iC3b fragment of the third complement component.
• Integrin β-3, which associates with α-IIB to form a receptor for fibrinogen, fibronectin, vitronectin and VWF, and with α-V to form a vitronectin receptor.
• Integrin β-4, which associates with α-6.
• Integrin β-5, which associates with α-V.
• Integrin β-6 [3].
• Integrin β-7 [4].
• Integrin β-8, which associates with α-V [5].
• The Drosophila myospheroid protein, a probable integrin β chain.

All the integrin β chains contain four repeats of a forty amino acid region in the C-terminal extremity of their extracellular domain. Each of the repeats contains eight cysteines. We have developed a pattern from a section of the repeated region that includes five of these conserved cysteines.