A chain
Definition:
- the shorter polypeptide component of insulin containing 21 amino acyl residues, beginning with a glycyl residue (NH2-terminus); insulin consists of an A chain linked to a B chain by two disulfide bonds; the amino-acid composition of the A chain is a function of species;
- in general, one of the polypeptides in a multiprotein complex.
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Examples: glitazone, GI cocktail, etc.

