Identification and characterization of the Poa p IX group of basic allergens of Kentucky bluegrass pollen
1991
Olsen, E. | Zhang, L. | Hill, R.D. | Kisil, F.T. | Sehon, A.H. | Mohapatra, S.S.
We reported previously the primary structure of three full-length cDNA clones that encode a new group of IgE-binding proteins of Kentucky bluegrass (KBG) pollen, designated as Poa p IX. In the present study we have further characterized the cloned Poa p IX proteins, identified the corresponding proteins in KBG pollen extract, and determined their antigenic relationships with other known grass pollen allergens. A recombinant IgE-binding polypeptide rKBG7.2 that represents the C-terminal fragment, conserved in Poa p IX proteins, appeared to contain epitopes unique to these proteins and served as an immunosorbent for the isolation of the corresponding human IgE antibodies. On two-dimensional PAGE blots these IgE antibodies bound selectively to five distinct KBG pollen proteins with molecular mass 28 to 34 kDa and isoelectric point > 9.5. These proteins differ in size and charge from known allergens, but are very similar to those of the recombinant Poa p IX proteins. The rKBG3.1, which represents the N-terminal region of the Poa p IX clone KBG31, as well as the corresponding natural allergens were shown to possess epitopes that crossreact with the acidic group V allergens of Timothy. Comparison of amino acid sequences of recombinant Poa p IX proteins with those of Lol p I isoallergens revealed no significant sequence similarities. In contrast, partial homology was demonstrated between the N-terminal sequences of these proteins and the Phl p V proteins. Our results confirm that the Poa p IX clones represent a distinct and major group of allergens of KBG pollen, and demonstrate structural similarities and antigenic cross-reactivities among different groups of allergenic proteins in grass pollens.
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