An 8-residue polypeptide was determined to have the followin…
An 8-residue polypeptide was determined to have the following amino acid composition: (Met)2, Phe, Pro, Gln, Arg, Gly, Tyr. The first-round of Edman degradation released PTH-Gly. Both trypsin treatment and CNBr treatment yielded a tripeptide and a pentapeptide, respectively (with different sequences). Digestion with chymotrypsin (note: only consider cleavage next to aromatic amino acids) produced a tetrapeptide, a tripeptide and a free methionine. The amino acid sequence of this octapeptide should be:
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