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| 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. SP-1 SP-2 T-1 T-2 CT-7 |
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