Biophys J, September 2000, p. 1601-1609, Vol. 79, No. 3

Homology Modeling and Characterization of IgE Binding Epitopes of Mountain Cedar Allergen Jun a 3

Kizhake V. Soman,^* Terumi Midoro-Horiuti, Josephine C. Ferreon,^* Randall M. Goldblum, Edward G. Brooks, Alexander Kurosky,^* Werner Braun,^* and Catherine H. Schein^*

 ^*Sealy Center for Structural Biology and Department of Human Biological Chemistry and Genetics, and  Department of Pediatrics, Child Health Research Center, University of Texas Medical Branch, Galveston, Texas 77555-1157 USA

The Jun a 3 protein from mountain cedar (Juniperus ashei) pollen, a member of group 5 of the family of plant pathogenesis-related proteins (PR-proteins), reacts with serum IgE from patients with cedar hypersensitivity. We used the crystal structures of two other proteins of this group, thaumatin and an antifungal protein from tobacco, both ~50% identical in sequence to Jun a 3, as templates to build homology models for the allergen. The in-house programs EXDIS and FANTOM were used to extract distance and dihedral angle constraints from the Protein Data Bank files and determine energy-minimized structures. The mean backbone deviations for the energy-refined model structures from either of the templates is <1 Å, their conformational energies are low, and their stereochemical properties (determined with PROCHECK) are acceptable. The circular dichroism spectrum of Jun a 3 is consistent with the postulated -sheet core. Tryptic fragments of Jun a 3 that reacted with IgE from allergic patients all mapped to one helical/loop surface of the models. The Jun a 3 models have features common to aerosol allergens from completely different protein families, suggesting that tertiary structural elements may mediate the triggering of an allergic response.

Biophys J, September 2000, p. 1601-1609, Vol. 79, No. 3
© 2000 by the Biophysical Society   0006-3495/00/09/1601/09  $2.00

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