Amino acids 1-12 (AGGKSGKDSGKV) are replaced with amino acids 1-10 (SGRGKGGKV) of His2A. This region at the N terminal end, before the αN helix, is converted into the equivalent region in His2A.
The lethality associated with His2Av810 is partially rescued by His2AvtM1. At 25oC all flies reach pupariation, and about 50% of flies are rescued to adulthood. At 29oC about a third are rescued to adulthood.