Myoglobins of Cartilaginous Fishes. II. Isolation and Amino Acid Sequence of Myoglobin of the Shark Mustelus Antarcticus

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Abstract
Myoglobin isolated from red muscle of the gummy shark M. antarcticus was purified by gel filtration and ion-exchange chromatography on CM-cellulose in 8 M urea-thiol buffer. Amino acid analysis and sequence determination showed 148 amino residues. The amino terminal residue is acetylated as shown by NMR and mass spectrographic analysis of an N-terminal peptide. There is a deletion of 4 residues at the amino terminal end as well as 1 residue in the CD interhelical area relative to other myoglobulins. These overall differences were also found previously in myoglobin of Heterodontus portusjacksoni. The complete amino acid sequence has been determined following digestion with trypsin, chyomatrypsin, thermolysin, staphylococcal protease and cyanogen bromide. Sequences of purified peptides were determined by the dansyl-Edman procedure. The amino acid sequence showed approximately 88 differences from mammalian, monotreme, bird and tuna myoglobins, slightly more than previously reported for H. portusjacksoni, usually considered a more primitive animal. There were 24 residues common to both shark myoglobins that were different from those present in other myoglobins. The sequence was compared to the myoglobin of yellowfin tuna and other myoglobins.

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