Spectrin in Erythrocytes
The convenience of using erythrocytes compared to other cell types means they have become the standard model for the investigation of the spectrin cytoskeleton. Dimeric spectrin is formed by the lateral association of αI and βI monomers to form a dimer. Dimers then associate in a head-to-head formation to produce the tetramer. End-to-end association of these tetramers with short actin filaments produces the hexagonal complexes observed.
In humans, association with the intracellular face of the plasma membrane is by indirect interaction, through direct interactions with protein 4.1 and ankyrin, with the transmembrane ion transporter band 3 Protein 4.2 binds the spectrin tail region to the transmembrane protein glycophorin A. In animals, spectrin forms the meshwork that provides red blood cells their shape.
The erythrocyte model demonstrates the importance of the spectrin cytoskeleton in that mutations in spectrin commonly cause hereditary defects of the erythrocyte, including hereditary elliptocytosis and hereditary spherocytosis.
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