Biochemical analysis of the interaction of calcium with toposome: A major protein component of the sea urchin egg and embryo

We have investigated the biochemical and functional properties of toposome, a major protein component of sea urchin eggs and embryos. Atomic force microscopy was utilized to demonstrate that a Ca2+‐driven change in secondary structure facilitated toposome binding to a lipid bilayer. Thermal denatura...

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Bibliographic Details
Published in:Journal of cellular biochemistry 2008-04, Vol.103 (5), p.1464-1471
Main Authors: Hayley, Michael, Sun, Ming, Merschrod S, Erika F., Davis, Philip J., Robinson, John J.
Format: Article
Language:English
Subjects:
Animals
calcium
Calcium - chemistry
Calcium - metabolism
Cations, Divalent - chemistry
Cations, Divalent - metabolism
Egg Proteins - chemistry
Egg Proteins - metabolism
Embryo, Nonmammalian - chemistry
Embryo, Nonmammalian - metabolism
Glycoproteins - chemistry
Glycoproteins - metabolism
membrane-membrane interaction
Metals - chemistry
Metals - metabolism
Microscopy, Atomic Force
Ovum - chemistry
Ovum - metabolism
Protein Binding - physiology
Protein Structure, Quaternary
Protein Structure, Secondary
sea urchin
Strongylocentrotus purpuratus - chemistry
Strongylocentrotus purpuratus - metabolism
toposome
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Summary:We have investigated the biochemical and functional properties of toposome, a major protein component of sea urchin eggs and embryos. Atomic force microscopy was utilized to demonstrate that a Ca2+‐driven change in secondary structure facilitated toposome binding to a lipid bilayer. Thermal denaturation studies showed that toposome was dependent upon calcium in a manner paralleling the effect of this cation on secondary and tertiary structure. The calcium‐induced, secondary, and tertiary structural changes had no effect on the chymotryptic cleavage pattern. However, the digestion pattern of toposome bound to phosphatidyl serine liposomes did vary as a function of calcium concentration. We also investigated the interaction of this protein with various metal ions. Calcium, Mg2+, Ba2+, Cd2+, Mn2+, and Fe3+ all bound to toposome. In addition, Cd2+ and Mn2+ displaced Ca2+, prebound to toposome, while Mg2+, Ba2+, and Fe3+ had no effect. Collectively, these results further enhance our understanding of the role of Ca2+ in modulating the biological activity of toposome. J. Cell. Biochem. 103: 1464–1471, 2008. © 2007 Wiley‐Liss, Inc.
ISSN:0730-2312
1097-4644
DOI:10.1002/jcb.21531