N-Terminal Sequence of Human Big Gastrin: Sequence, Synthetic and Immunochemical Studies

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Abstract
The previously assigned structure of human big gastrin is revised as a result of sequencing and immunological studies on synthetic peptides. A nonadecapeptide was synthesized and has full immunochemical potency compared with natural human G34 in a radioimmunoassay which is specific for the N-terminal sequence. Syntheses of the peptides were achieved using the stepwise procedure with benzyloxycarbonylamino acids and fragment couplings mediated mainly by the dicyclohexylcarbodiimide procedure in the presence of either N-hydroxysuccinimide or 1-hydroxybenzotriazole. Purification of the peptide fragments was by Sephadex LH-20 chromatography and removal of protecting groups was effected using 90% trifluroacetic acid in the presence of scavengers. Purification of the nonadecapeptide was achieved by high performance liquid chromatography.