INIBIOLP   05426
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE LA PLATA "PROF. DR. RODOLFO R. BRENNER"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
pH stability and Low Resolution Structure of Ovorubin, a protease inhibitor from the eggs of Pomacea canaliculata
Autor/es:
ITUARTE,S.; DREON, M.S.; CEOLIN,M.; HERAS, H.
Lugar:
Acapulco, Mexico
Reunión:
Congreso; 2nd Latin American Protein Society Meeting; 2007
Institución organizadora:
2nd Latin American Protein Society Meeting
Resumen:
Ovorubin is a 300 KDa thermostable protease inhibitor and the major egg protein of the snail Pomacea canaliculata. It is a glyco-lipo-carotenoprotein containing the carotenoid astaxanthin as a prosthetic group. Here we report ovorubin dimensions and global shape and analyze the effect of pH on stability, using small angle X-ray scattering (SAXS), electron microscopy (EM), circular dichroism, fluorescence and absorption spectroscopy. Analysis of the scattering data and estimation of the shape showed that the protein fits into an ellipsoid with an axial length of 69 Å and a radius of 43 Å. The diameter obtained by EM (102 Å) agrees with the maximum pair distance obtained from SAXS results. Quaternary structure was only affected at pH values below 4 showing a reduction in its giration radius and loss of tertiary structure. The absorption spectra and CD of ovorubin at pH values between 2 - 12, showed no significant changes in its intensity or shape, indicating that astaxanthin binding was not affected. Taken together these results indicate that low pH values are triggering the disassembling, but not the unfolding of the oligomer. Ovorubin is therefore the carotenoprotein with the highest stability against pH reported for invertebrates. Considering the wide-range pH stability and the protease inhibitor function, it could very well be that ovorubin is actively involved in the chemical defence of embryos by limiting the predator’s ability to digest and use essential nutrients from the eggs, thus rendering the ingestion of eggs antinutritive.