An exceptional amino acid replacement on the distal side of the iron atom in proboscidean myoglobin.

Amino acid sequence determination of elephant myoglobin revealed the presence of the unusual substitution E7 His leads to Gln. Stereochemical analyses suggest that the most suitable residue which can functionally substitute for His at this position in vertebrate globins is Gln. Physiochemical studies imply that the slower rate of autooxidation of elephant myoglobin is the result of this substitution which may confer some selective advantage on the species. Comparative sequence data of paenungulate myoglobins suggest that the His leads to Gln mutation probably occurred in an ancestor of Elephantinae.