Share
Explore BrainMass

Integrin and Extracellular matrix

You must answer the questions. 600 words each question. . Use diagrams to illustrate with the explanation? . The questions are all essay- type. read them carefully and make sure you answer the question posed.

1. Discuss the structure and function of integrins using diagrams to illustrate your answer

2. 'Extracellular matrix simply fills the gaps between cells in connective tissues'. Discuss this statement in the light of current knowledge of extracellular matrix.

Solution Preview

Discuss the structure and function of integrins using diagrams to illustrate your answer

Integrins are transmembrane cell adhesion proteins that function to attach the extracellular matrix to the cell's cytoskeleton. (1) They are matrix receptors found mostly in animal cells. They are composed of a large family of homologous "transmembrane, cell matrix adhesion receptors." (1) Integrin also serve as cell to cell adhesion molecules and help the cells bind to other cells, as well as the extracellular matrix. (1) Unlike other cell surface receptors, integrins bind their ligand with lower affinity and are present at about tenfold to hundredfold higher concentration on the cell surface. (1) If integrin binding to cells were too tight, cells would stick to the extracellular matrix and cannot move. Integrin has other functions beside binding to a cell to its surroundings. Integrins activate intracellular signaling pathways that communicate with the cell. (1)

Integrins are the main receptor proteins that cells use to both bind to and respond to the extracellular matrix. An integrin molecule is "composed of two noncovalently associated transmembrane glycoprotein subunits called α and β." (1) The extracellular divalent cation (Ca2+ and Mg2+) dictate how integrin binds to their ligands. (1) The type of divalent cation influence both the affinity and the specificity of binding of an integrins to its ligands.

The integrin molecule look like the structure above. The globular head "projecting more than 20 nm from the lipid bilayer." (1) Integrin bind to matrix protein outside the cell , and it also to actin cytoskeleton via the anchor protein inside the cell."(1) It serves as the transmembrane linker. The α and β subunits are held together by noncovalent bonds. The "α subunit is made initially as single 140K Dalton polypeptide chain, which is then cleaved into one small transmembrane domain, and one large extracellular domain that contain four divalent cation binding sites." (1) The two domains are held together by disulfide bond.

Integrins bind to many matrix proteins in verterbrates. For example, about "8 integrins bind fibronectin, and 5 bind laminin." (1) Human integrin heterodimers are "formed from 9 types of B subunits and 24 types of α subunits. " (1) β1 subunits form "dimmers with at least 12 distinct α subunits." (1) These are found in almost all vertebrates cells: "α5B1 is a ...

Solution Summary

Integrins are transmembrane cell adhesion proteins that function to attach the extracellular matrix to the cell's cytoskeleton. (1) They are matrix receptors found mostly in animal cells. They composed of a large family of homologous transmembrane, cell matrix adhesion receptors. Integrin also serve as cell-cell adhesion molecules and help the cells bind to other cells, as well as the extracellular matrix.

$2.19