Calcium binding properties of recombinant calcium binding protein 40, a major calcium binding protein of lower eukaryote Physarum polycephalum.
Biochemistry
; 39(13): 3827-34, 2000 Apr 04.
Article
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| MEDLINE
| ID: mdl-10736183
Calcium binding protein 40 (CBP40) is a Ca(2+)-binding protein abundant in the plasmodia of Physarum polycephalum. CBP40 consists four EF-hand domains in the COOH-terminal half and a putative alpha-helix domain in the NH(2)-terminal half. We expressed recombinant proteins of CBP40 in Escherichia coli to investigate its Ca(2+)-binding properties. Recombinant proteins of CBP40 bound 4 mol of Ca(2+) with much higher affinity (pCa(1/2) = 6.5) than that of calmodulin. When residues 1-196 of the alpha-helix domain were deleted, the affinity for Ca(2+) decreased to pCa(1/2) = 4.6. A chimeric calmodulin was generated by conjugating the alpha-helix domain of CBP40 with calmodulin. The affinity of Ca(2+) for the chimeric calmodulin was higher than that for calmodulin, suggesting that the alpha-helix domain is responsible for the high affinity of CBP40 for Ca(2+). CBP40 forms large aggregates reversibly in a Ca(2+)-dependent manner. A mutant protein with a deletion of NH(2)-terminal 32 residues, however, could not aggregate, indicating the importance of these residues for the aggregation. The aggregation occurs above micromolar levels of Ca(2+) concentration, so it may only occur when CBP40 is secreted out of the plasmodial cells.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Physarum
/
Proteínas Recombinantes de Fusión
/
Proteínas de Unión al Calcio
/
Proteínas Protozoarias
Límite:
Animals
Idioma:
En
Revista:
Biochemistry
Año:
2000
Tipo del documento:
Article
País de afiliación:
Japón
Pais de publicación:
Estados Unidos