Amino acids 36-45 (HLKSRTTSHG) are replaced with amino acids 33-41 (LLRKGNYAE) of His2A. This region starting at the C terminal end of the α1 helix, and continuing into loop 1 is converted into the equivalent region in His2A.
The lethality associated with His2Av810 is partially rescued by His2AvtM3. At 25oC all flies reach pupariation, and about 90% of flies are rescued to adulthood. At 29oC about 90% are rescued to adulthood.