Sequence polymorphism of the group 1 allergen of Bermuda grass pollen

Abstract

Background: Cyn d 1, the major allergen of Bermuda grass pollen, consists of a number of isoforms. Objective: To examine the extent of sequence variation of Cyn d 1 isoforms at the molecular level. Methods: A Bermuda grass pollen λZAP II cDNA expression library was immunoscreened with anti-Cyn d 1 monoclonal antibodies. The reactive clones were isolated, subcloned into Escherichia coli, and sequenced. Some of them were expressed in the yeast Pichia pastoris to obtain recombinant Cyn d 1 proteins. Results: Ten cDNA clones were obtained, all these clones encode the full length of Cyn d 1 protein. Their deduced mature proteins can be grouped into: the long ones with 246 amino acids, and the short ones with 244 amino acids. The last two amino acids (AG) of the long Cyn d 1 are deleted in the short Cyn d 1. The remaining amino acid sequences share more than 98% identity; a total of nine amino acid variations were observed. Two recombinant Cyn d 1 proteins (rCyn d 3-2 and rCyn d 5-4) with three amino acid substitutions showed differential IgE-binding profiles. Conclusion: The present study extended our understanding of the primary structure of isoforms of Cyn d 1.