CIRCULAR-DICHROISM (CD) STUDIES ON BIOLOGICAL-ACTIVITY OF MAST-CELL DEGRANULATING (MCD) PEPTIDE ANALOGS

Analogs of MCD peptide were synthesized by solid-phase methods. Positive charges were deleted at the N- and/or C-terminus, including the helical portion of the molecule. Four peptides were prepared by removing residues 16-18 (Arg-Lys-Ile), 1-2 (Lys), 1-2 and 16-18 and by acetylation of the amino end (Ile), Analogs were tested on mast cells for histamine-releasing activity. Although the helicity of these derivatives, determined by circular dichroism (CD), was not significantly different from the native MCD peptide, two analogs with C-terminal deletions showed a 5- to 10-fold decrease in activity. These findings suggest that the C-terminus is more important than the N-terminus in determining bioactivity of MCD peptide. (C) Munksgaard 1994.