Question

6. The sequence of kassinin, a tachykinin dodecapeptide from the African frog Kassina senegalensis, was determined. A single round of Edman degradation identifies Asp as the N-terminus. A second sample of the peptide is treated with chymotrypsin. Two fragments are released with the following amino acid compositions: fragment I (Gly, Leu, Met, Val) and fragment II (Asp2, Gln, Lys, Phe, Pro, Ser, Val). Next, a third sample of peptide is treated with trypsin, which results in two fragments with the following amino acid compositions: fragment III (Asp, Pro, Lys, Val) and fragment IV (Asp, Gln, Gly, Leu, Met, Phe, Ser, Val). Treatment of another sample with elastase yields a single Gly residue and three fragments—fragment V (Leu, Met), fragment VI (Asp, Lys, Pro, Ser, Val), and fragment VII, which was sequenced: Asp– Gln–Phe–Val. A fourth sample was treatedwith CNBr, but the dodecapeptide was not cleaved. What is the sequence of the dodecapeptide?

Answer 1

Edman degradation Give N-terminus Chymotrypsin cleanes at Phenyl alanune Asp - - - - - - Phet ---- trypson cleanes at lynne As += lyst at - a phe - 1. Met Elastase cleaves at C-terminus val, ser, alye ley or the here.. u Sealine Asb Pro val lys van Ass Gilophe, val Gly Leu Met so After treatment of CNBR dode cape phele at was not cleared it means Methionine is in last position . eu me . Asp pro val lys ser Asp Gin Phe val aly,