BMB Reports
- 제33권5호
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- Pages.391-395
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- 2000
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- 1976-670X(eISSN)
Functional Characterization of the Squid Calexcitin-2, a Calcium and GTP-binding Protein
- Park, Sae-Young (Department of Biology, Inha University) ;
- Nelson, Thomas J. (Lab of Adaptive Systems, NINDS, National Institutes of Health) ;
- Alkon, Daniel L. (Lab of Adaptive Systems, NINDS, National Institutes of Health) ;
- Kim, Jeong-Ho (Department of Biology, Inha University)
- 투고 : 2000.07.05
- 심사 : 2000.08.23
- 발행 : 2000.09.30
초록
Calexcitin, a calcium-binding protein, was previously cloned and functionally characterized in the squid Loligo pealei. We now report the cloning of a second form of Calexcitin, Calexcitin-2, found in the squid Todarodes pacificus optic lobe. Calexcitin-2 has a significantly different carboxyl terminal region than Calexcitin-1. It lacks the CAAX motif, which is a farnesylation site. The amino acid sequence of Calexcitin-2 shows an 84% identity with Calexcitin-1 and also displays a strong cross immunoreactivity. Western blotting shows that Calexcitin-2 was expressed exclusively in the optic lobe region of squid, but not in other body organs. Regardless of its lack of conserved regions for GTP-binding, Calexcitin-2 shows moderately low affinity GTP-binding and also shows dramatic conformational change induced by GTP-binding. Three possible GTP-binding region mutations, K142A, D144A, and K157A, did not change the G TP binding affinity. This raises the possibility that Calexcitin-2 may have a novel GTP-binding motif.