NH2-terminal dodecapeptide of porcine big gastrin: Revised sequence and confirmation of structure by immunochemical analysis

A revised sequence for the NH₂-terminal dodecapeptide of porcine big gastrin is described which differs from that originally reported in the inversion of His⁷ and Pro⁹ for Pro⁷ and His⁹. The immunochemical properties of a range of synthetic peptide fragments and analogs of the original and revised sequences of porcine big gastrin were examined with an antiserum raised to the natural porcine peptide. The pattern of immunoreactivity of these peptides indicates that the antiserum has specificity for the 4–9 region of big gastrin. The dodecapeptide with the revised sequence had full immunoreactive potency relative to natural porcine big gastrin, whereas the dodecapeptide with the original sequence had about 1000-fold lower immunoreactivity. It is proposed that the synthetic peptide with the revised, but not the original, sequence is compatible with the structure of big gastrin.