INFLUENCE OF ALPHA-MSH TERMINAL AMINO-ACIDS ON BINDING-AFFINITY AND BIOLOGICAL-ACTIVITY IN MELANOMA-CELLS

The influence of the terminal amino acids of alpha-MSH on its biologic al action in B16 murine melanoma cells has been systematically studied . Fragments of alpha-MSH lacking various sequences of terminal residue s were synthesized by solid-phase peptide synthesis and their binding affinity to melanoma cells was measured using a radioreceptor assay. B iological activity was determined by measuring both tyrosinase activit y and melanogenesis. The relative affinities and activities of the fra gments generally followed the same pattern as found previously in othe r assay systems (frog and lizard bioassay and Cloudman S91 mouse melan oma), with the three amino acids at each terminal not being essential for binding and biological activity, although the C-terminal amino aci ds 11-13 are more important than those in the N-terminus. The differen ces in biological activity between the fragments can be explained by t heir relative binding affinities for the receptor.