tailieunhanh - Báo cáo Y học: Properties of group I allergens from grass pollen and their relation to cathepsin B, a member of the C1 family of cysteine proteinases

Expansins are a family of proteins that catalyze pHdependent long-term extension of isolated plant cell walls. They are divided into two groups, a and b, the latter consisting of the grass group I pollen allergens and their vegetative homologs. Expansins are suggested to mediate plant cell growth by interfering with either structural proteins or the polysaccharide network in the cell wall. | Eur. J. Biochem. 269 2083-2092 2002 FEBS 2002 doi Properties of group I allergens from grass pollen and their relation to cathepsin B a member of the C1 family of cysteine proteinases Kay Grobe1 Marco Poppelmann2 Wolf-Meinhard Becker2 and Arnd Petersen2 1 University of California San Diego La Jolla USA 2Forschungszentrum Borstel Borstel Germany Expansins are a family of proteins that catalyze pH-dependent long-term extension of isolated plant cell walls. They are divided into two groups a and b the latter consisting of the grass group I pollen allergens and their vegetative homologs. Expansins are suggested to mediate plant cell growth by interfering with either structural proteins or the polysaccharide network in the cell wall. Our group reported papain-like properties of b-expansin of Timothy grass Phleum pratense pollen Phl p 1 and suggested that cleavage of cell wall structural proteins may be the underlying mechanism of expansin-mediated wall extension. Here we report additional data showing that b-expansins resemble ancient and modern cathepsin B which is a member of the papain C1 family of cysteine proteinases. Using the Pichia pastoris expression system we show that cleavage of inhibitory prosequences from the recombinant allergen is facilitated by its N-glycosylation and that the truncated activated allergen shows proteolytic activity resulting in very low stability of the protein. We also show that deglycosylated full-length allergen is not activated efficiently and therefore is relatively stable. Motif and homology search tools detected significant similarity between b-expansins and cathepsins of modern animals as well as the archezoa Giardia lamblia confirming the presence of inhibitory prosequences active site and other functional amino-acid residues as well as a conserved location of these features within these molecules. Lastly we demonstrate by site-directed mutagenesis that the conserved His104 residue is involved .

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