The melanocyte stimulating activity of N-nitroso-2-chloroethyl-carbamoyl derivatives of α-melanotropin fragments

Abstract

A number of N-nitroso-2-chloroethyl-carbamoyl (Q(NO)) derivatives of α-melanotropin fragments have been synthesized and their effect on the frog skin melanocytes studied. Peptides substituted in this way possess the biological activity of the parent compounds, indicating that they preserved their receptor recognizing ability. These compounds can therefore serve as affinity labels. Some of these derivatives, related to the C-terminal sequence of α-melanotropin show prolonged darkening reaction, which does not influence the subsequent reaction of melanocytes with α-melanotropin. The Q(NO)-derivative of a fragment derived from the classical active site of the hormone shows, however, inhibition of the effect of α-melanotropin. It can be concluded that the latter peptide acts through the melanotropin receptor, while others, related to the C-terminal sequence of the hormone through another mechanism.