INSECT IMMUNITY .5. PURIFICATION AND SOME PROPERTIES OF IMMUNE PROTEIN-P4 FROM HEMOLYMPH OF HYALOPHORA-CECROPIA PUPAE

Previously we have shown that immunization of diapausing pupae of Hyalophora cecropia with viable non-pathogenic bacteria, gives rise to a simultaneous induction of an antibacterial activity and the selective synthesis of eight polypeptides designated P1-P8 (Faye et al., 1975). We have also shown that the major components, P4 and P5 were separated by a series of ammonium sulphate precipitations. Starting from the last of the ammonium sulphate precipitates we describe here the purification of immune protein P4 using isoelectric focusing. The purified material was homogenous in analytical polyacrylamide gel electrophoresis and was found to be composed of a single polypeptide chain with a molecular weight of 48,000. With rabbit antiserum to P4, cross-reacting material was found in both normal haemolymph and in tissue homogenate from immunized pupae. We have been unable so far to find a function for protein P4. © 1979.