THE Jonmn~ OF BIOLOGICAL CHEMIFJTRY

Tryptic and chymotryptic digests of human myoglobin have been separated chromatographically to give 23 pure tryptic peptides and 18 pure chymotryptic peptides. The complete or partial amino acid sequences of these peptides have been established. From the overlaps in sequence between chymotryptic and tryptic peptides it is possible to place 124 of the 152 residues of human myoglobin in a unique sequence. The remaining residues have been ordered tentatively on the basis of the apparent homology in sequence between human and sperm whale myoglobins. Human myoglobin appears to contain 152 residues instead of 153 residues as found in whale myoglobin. The sequence of human myoglobin appears to be accommodated easily into the proposed threedimensional structure of whale myoglobin, and large differences in the conformation of these two myoglobins cannot be expected.