Homoserine31]-Salmon Calcitonin I: Fully Active Analogue of Calcitonin Synthesized by Recombinant DNA Techniques

Abstract

We have made an active analogue of salmon calcitonin I, [homoserine 31]–salmon calcitonin I, by recombinant DNA and chemical techniques. First a calcitonin precursor, the [homoserine31]–salmon calcitonin I–(1–31) lactone, was obtained from a multi–copy fusion protein upon cyanogen bromide cleavage. The protein was expressed from a multiple–copy salmon calcitonin I gene fused to lacZ. The C–terminal homoserine was reacted with prolinamide to get the 32 amino acid peptide, [homoserine31]–salmon calcitonin I. This analogue was equipotent to the naturally–occurring salmon calcitonin I in lowering plasma calcium levels in a rat bioassay. This method thus offers an opportunity to make C–terminal amides through intermediates made by recombinant DNA methods.