A peptide (hereafter called peptide CT-7) was recovered from a
chymotryptic digest of a protein and was isolated in pure form. When treated with strong
acid and at high temperature it was totally hydrolyzed into its constituent amino acids
which where determined to be alanine, aspartic acid, histidine, lysine, phenylalanine,
proline, and threonine in equimolar amounts (listed alphabetically).
When a staphylococcal protease digest of CT-7 was fractionated by passage over
a gel filtration column two peptides were recovered (SP-1 and SP-2). When the
material of the first peak to be eluted from the column (SP-1) was subjected to
electrophoresis at pH 5.8 it migrated toward the cathode. Application of the Edman
degradation to SP-1 yielded the PTH of histidine in the first round and the PTH of lysine
in the second round. The peptide in the second peak eluted from the column (SP-2) was
found to absorb light in the ultraviolet region of the spectrum and was immobile when
subjected to electrophoresis at pH 5.8. The amino terminal residue of SP-2 was
determined to be proline.
When CT-7 was digested with trypsin it yielded two products, T-1 and T-2.
These digestion products could be separated on a gel filtration column. The first
material eluted (T-1) absorbed ultraviolet light and was anionic when electrophoresed at
pH 5.8. Edman degradation of this peptide yielded the phenylthiohydantoin of alanine in
the first round of degradation and the phenylthiohydantoin of threonine in the second
round of degradation. Peptide T-2 was cationic when electrophoresed at pH 5.8 and
also at pH 9.
What are the sequences of the peptides? Use the standard conventions for
designating sequences. Use either the single or three letter abbreviations to designate the
amino acid residues.