Transduction of Ca2+ signals upon fertilization of eggs; identification of an S-100 protein as a major Ca(2+)-binding protein.
A transient increase in the level of free cytosolic Ca2+ is observed upon fertilization of the eggs of many species and is thought to represent a key event in the initiation of development. To identify components in the egg which could be involved in mediating such Ca2+ signals we searched for Ca(2+)-binding proteins in eggs of the fresh-water fish Misgurnus fossilis (loach). We show that loach eggs contain two major Ca(2+)-binding proteins which can be purified through their Ca(2+)-dependent interaction with a hydrophobic matrix. Protein sequencing revealed that the larger 18 kDa protein is calmodulin, while the smaller polypeptide of 10 kDa is a member of the S-100 protein family. This is the first report of the presence of an S-100 protein in vertebrate eggs and shows that this protein is found in two fold higher concentration than calmodulin. Since the 10 kDa protein shares 68% sequence identity with S-100 alpha from bovine brain, it can be considered as the loach homologue of mammalian S-100 alpha. During early embryonic development, de novo protein synthesis of calmodulin is observed at the earliest stages analyzed (mid-blastula), while de novo protein synthesis of the S-100 alpha homologue begins with the mid-gastrula stage.(ABSTRACT TRUNCATED AT 250 WORDS)
Ivanenkov
V V
VV
Max Planck Institute for Biophysical Chemistry, Department of Biochemistry, Goettingen, Germany.
Gerke
V
V
Minin
A A
AA
Plessmann
U
U
Weber
K
K
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000032:analysis*; D003531:Cypriniformes / Q000378:metabolism*; D004527:Egg Proteins / Q000032:analysis*; D005306:Fertilization / Q000502:physiology*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000502:physiology*
D002135:Calcium-Binding Proteins; D004527:Egg Proteins; D002118:Calcium