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
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.
The pattern will not pick up the first of the four repeats, the spacing
of the cysteine residues being different in that repeat.
May 2004 / Text revised.
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