tailieunhanh - Báo cáo khoa học: Global shape and pH stability of ovorubin, an oligomeric protein from the eggs of Pomacea canaliculata

Ovorubin, a 300-kDa thermostable oligomer, is the major egg protein from the perivitellin fluid that surrounds the embryos of the apple snail Poma-cea canaliculata. It plays essential roles in embryo development, including transport and protection of carotenoids, protease inhibition, photoprotec-tion, storage, and nourishment. | ễFEBS Journal Global shape and pH stability of ovorubin an oligomeric protein from the eggs of Pomacea canaliculata Marcos S. Dreon1 Santiago Ituarte1 Marcelo Ceolin2 and Horacio Heras1 1 Institute de Investigaciones Bioquimicas de La Plata INIBIOLP CONICET-UNLP Argentina 2 Institute de Investigaciones Fisico-Quimicas Teoricas y Aplicadas INIFTA CONICET-UNLP La Plata Argentina and Universidad Nacional del Noroeste de Buenos Aires Pergamino Argentina Keywords carotenoprotein mollusk protease inhibitor protein stability protein structure Correspondence H. Heras INIBIOLP - Fac. Cs. Medicas 60 y 120 La Plata 1900 Argentina Fax 54 221 4258988 Tel 54 221 4824894 E-mail h-heras@ Received 16 May 2008 revised 3 July 2008 accepted 11 July 2008 doi Ovorubin a 300-kDa thermostable oligomer is the major egg protein from the perivitellin fluid that surrounds the embryos of the apple snail Poma-cea canaliculata. It plays essential roles in embryo development including transport and protection of carotenoids protease inhibition photoprotection storage and nourishment. Here we report ovorubin dimensions and global shape and test the role of electrostatic interactions in conformational stability by analyzing the effects of pH using small-angle X-ray scattering SAXS transmission electron microscopy CD and fluorescence and absorption spectroscopy. Analysis of SAXS data shows that ovorubin is an anisometric particle with a major axis of 130 A and a minor one varying between 63 and 76 A. The particle shape was not significantly affected by the absence of the cofactor astaxanthin. The 3D model presented here is the first for an invertebrate egg carotenoprotein. The quaternary structure is stable over a wide pH range . At a pH between and a reduction in the gyration radius and a loss of tertiary structure are observed although astaxanthin binding is not affected and only minor alterations in secondary structure are .