Four new monomeric insulins obtained by alanine scanning the dimer-forming surface of the insulin molecule.

The residues A21Asn, B12Val, B16Tyr, B24Phe, B25Phe, B26Tyr and B27Thr, buried in the dimer of insulin, were identified by means of alanine-scanning mutagenesis. The receptor binding activity, in vivo biological potency and self-association properties of the seven single alanine human insulin mutants were determined. Four of the seven single alanine mutants, [B12Ala]human insulin, [B16Ala]human insulin, [B24Ala]human insulin and [B26Ala]human insulin, are monomeric insulin, which indicates that B12Val, B16Tyr, B24Phe and B26Tyr are crucial for the formation of insulin dimer. The monomeric [B16Ala]human insulin and [B26Ala]human insulin retain 27 and 54% receptor binding activity, respectively, and nearly the same in vivo biological potency compared with native insulin, so they could be developed as the fast-acting insulin.