Abstract
Interleukin 1 (IL-1) is a major immunoregulatory protein released by macrophages with many host defense related properties. That IL-1 has been found in the invertebrates attests to its importance in homeostasis.The first step in comparing the vertebrate protein to its invertebrate correlate is to purify the protein to study. We have purified to homogeneity IL-1 isolated from the coelomic fluid of the starfish Asterias forbesi. The IL-1 had isoelectric points of 7.4, 5.4 and 4.8. The pI 4.8 species had a molecular weight of 22,000 and the pI 7.4 and 5.4 species both had M r of 17,000. Higher M r forms were also found. These molecules were biologically active in the human melanoma A375 cytotoxity assay for IL-1, and were also able to stimulate murine dermal fibroblast proliferation, protein synthesis, and PGE 2 production. The pI 4.8 and 5.4 forms were purified to homogeneity and the amino acid composition was determined. The pI 4.8 and 5.4 species were purified more than 200-fold to specific activities of 3 × 10 6 and 1 × 10 6 units mg −1, respectively. The pI 7.4 form was isolated and partial N-terminal sequence analysis was performed. The similarities of molecular weight, isoelectric points and biological properties between verebrate and invertebrate IL-1 show that it is an important, evolutionarily stable host defense molecule.
Published Version
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