Grass group I allergens (beta-expansins) are novel, papain-related proteinases.
Expansins are a family of proteins that catalyse long-term extension of isolated plant cell walls due to an as yet unknown biochemical mechanism. They are divided into two groups, the alpha-expansins and beta-expansins, the latter group consisting of grass group I allergens and their vegetative homologs. These grass group I allergens, to which more than 95% of patients allergic to grass pollen possess IgE antibodies, are highly immunologically crossreactive glycoproteins exclusively expressed in pollen of all grasses. Alignments of the amino-acid sequences of grass group I allergens derived from diverse grass species reveal up to 95% homology. It is therefore likely that these molecules share a similar biological function. The major grass group I allergen from timothy grass (Phleum pratense), Phl p 1, was chosen as a model glycoprotein and expressed in the methylotrophic yeast Pichia pastoris to obtain a post-translationally modified and functionally active allergen. The recombinant allergen exhibited proteolytic activity when assayed with various test systems and substrates, which was also subsequently demonstrated with the natural protein, nPhl p 1. These observations are confirmed by amino-acid alignments of Phl p 1 with three functionally important sequence motifs surrounding the active-site amino acids of the C1 (papain-like) family of cysteine proteinases. Moreover, the significantly homologous alpha-expansins mostly share the functionally important C1 sequence motifs. This leads us to propose a C1 cysteine proteinase function for grass group I allergens, which may mediate plant cell wall growth and possibly contributes to the allergenicity of the molecule.
Grobe
K
K
University of California, La Jolla, CA, USA. kgrobe@popmail.ucsd.edu
Becker
W M
WM
Schlaak
M
M
Petersen
A
A
D000485:Allergens / Q000737:chemistry* / Q000235:genetics; D000595:Amino Acid Sequence; D001483:Base Sequence; D016384:Consensus Sequence; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000276:immunology*; D017931:DNA Primers / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D010206:Papain / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D010843:Pichia / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology*; D006109:Poaceae / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D011058:Pollen / Q000737:chemistry* / Q000235:genetics / Q000276:immunology*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D006255:Rhinitis, Allergic, Seasonal / Q000276:immunology; D017386:Sequence Homology, Amino Acid
D000485:Allergens; D017931:DNA Primers; D010940:Plant Proteins; D011994:Recombinant Proteins; C095825:expansin protein, plant; C090396:PHLPI protein, Phleum pratense; D003546:Cysteine Endopeptidases; D010206:Papain