The major allergen (designated as Par h 1) was purified from the pollen of Parthenium hysterophorus (a major cause of allergic rhinitis) using anion exchange chromatography and HPLC. The purified protein was homogenous on SDS-PAGE and revealed a single N-terminal amino acid (lysine) upon Edman degredation. Par h 1 was a glycoprotein, rich in glycine and proline, and with an estimated molecular weight of 31 kd. Isoallergens were observed with pI values from 4.3 to 5.2. The carbohydrate moieties on Par h1 appeared related to its IgE binding ability. The N-terminal 91 amino acid sequence of Par h 1 shows 81% identity with a protein from sunflower anther and the hydroxyproline-rich region of Par h 1 is 30-40% identical to similar stretches in extensins. IgE antibodies in the sera of Parthenium allergic individuals cross-reacted with a 50 kd hydroxyproline-arabinose-rich extensin from potato tuber. Thus, it appears that a group of soluble plant glycoproteins related to extensins, have carbohydrate-containing IgE binding epitopes that may contribute to allergenic cross-reactivity among specific pollens and foods.
