Nature of the B10 amino acid residue.

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Abstract
Human [10-asparagine-B] insulin ([Asn10-B] insulin), an analog which differs from the parent molecule in that the histidine residue at position 10 of the B chain (B10) is replaced by asparagine, was synthesized and isolated in purified form. In vitro biological assays indicated a potency of approximately 35% compared to insulin. The replacement of histidine at position B10 by lysine resulted in an analog displaying approximately 15% of the biological activity of natural hormone, while the substitution of leucine in this position produced a molecule exhibiting approximately 45% potency in in vivo assays. Molecular size of the amino acid residue at position B10 may be important in the maintenance of a structure commensurate with high biological activity. Polarity at this position appears to be rather unimportant while a strongly basic group appears to be deleterious.