Cloning, expression and characterization of a novel four EF-hand Ca 2+-binding protein from olive pollen with allergenic activity

Abstract

A novel allergenic member of the family of Ca 2+-binding proteins has been cloned from olive tree pollen. The isolated DNA codes for a protein of 171 amino acid residues, which displays four EF-hand sequence motifs. The encoded protein was overproduced in Escherichia coli and purified. The protein (18 795 Da), which binds Ca 2+ and IgE antibodies from patients allergic to olive pollen, undergoes Ca 2+-dependent conformational changes. It is retained on a phenyl-Sepharose column, which indicates the existence of regulatory EF-hand domains. This fact suggests its involvement in Ca 2+-dependent signal transduction events of the pollen grain. This allergen could be considered as a member of a new subfamily of EF-hand Ca 2+-binding proteins since it displays a low amino acid sequence similarity with the so far known proteins.