J. Biol. Chem., Vol. 262, Issue 6, 2613-2623, Feb, 1987

The primary structure of a new Mr 18,000 calcium vector protein from amphioxus

T Kobayashi, T Takagi, K Konishi and JA Cox

The amino acid sequence of a new Ca2+-binding protein (CaVP) from Amphioxus muscle (Cox, J. A., J. Biol. Chem. 261, 13173-13178) has been determined. The protein contains 161 amino acid residues and has a molecular weight of 18,267. The N terminus is blocked by an acetyl group. The two functional Ca2+-binding sites have been localized based on homology with known Ca2+-binding domains, on internal homology and on secondary structure prediction, and appear to be the domains III and IV. The C-terminal half of CaVP, which contains the two Ca2+-binding sites, shows a remarkable similarity with human brain calmodulin (45%) and with rabbit skeletal troponin C (40%). Functional domain III contains 2 epsilon-N-trimethyllysine residues in the alpha-helices flanking the Ca2+-binding loop. Sequence determination revealed two abortive Ca2+-binding domains in the N-terminal half of CaVP with a similarity of 24 and 30% as compared with calmodulin and troponin C, respectively. This half is also characterized by the presence of a disulfide bridge linking the N-terminal helix of domain I to the C- terminal helix of domain II. This disulfide bond is very resistant to reduction in the native state, but not in denatured CaVP. The optically interesting aromatic chromophores (2 tryptophan and 1 tyrosine residues) are all located in the nonfunctional domain II.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				S. L. Hooper and J. B. Thuma Invertebrate Muscles: Muscle Specific Genes and Proteins Physiol Rev, July 1, 2005; 85(3): 1001 - 1060. [Abstract] [Full Text] [PDF]

				S. Baladi, P. O. Tsvetkov, T. V. Petrova, T. Takagi, H. Sakamoto, V. M. Lobachov, A. A. Makarov, and J. A. Cox Folding units in calcium vector protein of amphioxus: Structural and functional properties of its amino- and carboxy-terminal halves Protein Sci., April 1, 2001; 10(4): 771 - 778. [Abstract] [Full Text]