Solid-phase synthesis of the non-calcium-binding loop of cod allergen M. Direct evidence of the reactivity of the amino-terminal segment.

The synthesis of the non-calcium-binding AB loop of the assembly 13-32 of cod Allergen M (Mr 2122.1) was accomplished by solid-phase peptide synthesis. This peptide and the previously synthesized ones [12, 13, 14] have significant amino acid sequence homology. The synthetic crude preparation was obtained at relatively high recovery and purity. Further purification on a Bio-Gel P-2 column and a reversed-phase high-performance liquid chromatography column improved the grade of homogeneity, as demonstrated by high-voltage electrophoresis, end-terminal analysis, and amino acid composition. The peptide could, although to a much weaker extent than the intact Allergen M, directly bind IgE antibodies from the sera of cod-allergic individuals. At identical molar concentrations, a ratio of 1:6 for the in vitro reactivity of the peptide relative to the intact Allergen M was obtained. A similar reactivity was shown in the in vivo system used. The peptide also reacted with rabbit anti-Allergen M antibodies in rocket immunoelectrophoresis. The peptide appears to function as a divalent molecule in its primary interaction with antibodies.