A New Method for the Isolation of the (-Terminal Peptide of Proteins
183
Upon reaching this point, however it is clear that this methodology is not compatible with the Edman sequencing because the C-terminal peptide is obtained as
an N-terminal blocked species. In 1969, Butler et al. reported that the f amino
group of lysine residues in polypeptide chains could be reversibly blocked when
maleic anhydride is used. Since the chemical nature of the f amino group of
lysine and the amino terminal group of peptides are very close, in similar conditions, the maleyl group at the amino terminal group of the C-terminal peptide
should be also released. By this procedure, this strategy could be compatible with
the automatic sequencing.
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Fig. 12.5. Chromatograms A and B show a comparison between the rp-HPLC profIle of the native
and the succinylated cytochrome-Co The chromatograms C and D show the tryptic map of the succinylated Cytochrome C and the chromatogram obtained for the non retained fraction, respectively. E
is the FAB mass spectra of the major fraction obtained in D. Mal- and K* indicate the maleyl group
at the N -terminal end of the peptide and two succinyl residues within the sequence, respectively