A nonspecific, single-stranded nuclease activity with characteristics of a topoisomerase found in a major grass pollen allergen: possible biological significance.
The major allergen from timothy grass pollen, Phlp5b (Phleum pratense), was shown to exhibit ribonuclease activity. It turned out that the C-terminal portion of this molecule was the biologically active domain. Here evidence is presented that the allergen is a single-stranded, sugar-nonspecific nuclease with topoisomerase activity. An isomerase-specific active site was identified, and a non-active mutant was constructed by site directed mutagenesis, and showed no nucleolytic activity. In contrast to the wild type (WT), the mutant did not dimerize. Although the binding capacity of IgE antibodies toward the mutant was reduced as compared to the WT, the allergenic activity was retained. We conclude that the allergen Phlp5b is a single-stranded nuclease with an unusual topoisomerase-like activity. This biological activity is not by itself connected to the allergenicity of the molecule. Whether the enzymatic activity is responsible for the induction of the allergic sensitization and inflammation remains an open question.
Bufe
A
A
Pädiatrische Allergologie/Medizinische Klinik, Borstel, Germany.
Uhlig
U
U
Scholzen
T
T
Matousek
J
J
Schlaak
M
M
Weber
W
W
D000485:Allergens / Q000737:chemistry*; D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D006109:Poaceae / Q000276:immunology*; D011058:Pollen / Q000201:enzymology*; D017386:Sequence Homology, Amino Acid
D000485:Allergens; D004277:DNA, Single-Stranded; D004264:DNA Topoisomerases, Type I