Type II collagen is a homotrimer of three identical polypeptide (al) chains, each containing ~1000 amino acid residues. The designation al(II) indicates that the chain is from type II collagen. Because of the high content of the amino acid residues proline and hydroxyproline, and their stereochemistry, each al chain assumes a left-handed helical conformation (minor helix). Three a chains then wind around a common axis to form a right-handed superhelix (triple helix) in the native molecule. The al(II) chains can be isolated from native molecules by cation-exchange chromatography on carboxymethyl-cellulose following thermal denaturation. al(II) chains and cyanogen bromide fragments (see Support Protocol 3) are only useful for inducing arthritis when using the mouse CIA model. CIA in the rat model can only be achieved using native (triple-helical) CII.
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