COMPARATIVE-STUDIES OF FISH, AMPHIBIAN, AND REPTILIAN VITELLOGENINS

Plasma vitellogenins (VTGs) from estrogen-treated males of the common carp Cyprinus carpio, common frog Rana esculenta, crested newt Triturus carnifex, and lizard Podarcis sicula were purified by MgCl2-EDTA precipitation, DEAE cellulose chromatography, and ion-exchange FPLC. VTG isoelectric points and molecular weights of VTG subunits were determined by chromatofocusing and SDS-PAGE, respectively. Immune cross-reactivity was examined by ELISA with homologous and heterologous anti-VTG sera which were tested before and after purification by affinity chromatography with Sepharose-bound heterologous VTGs. Amphibian and reptilian VTGs contained both common and species specific antigenic determinant, whereas carp VTG was immunologically distinct and formed by subunits with smaller mass as compared to the monomeric VTGs of the other three species. The three-dimensional structure of VTG does not appear to be conserved during vertebrate evolution, probably because of differences in post-translational processing.