Phl p 3: structural and immunological characterization of a major allergen of timothy grass pollen.
BACKGROUND
The relevant importance of individual allergens for allergic sensitization is only partially understood. More detailed information on allergen structure and how it influences immunological responses can lead to better diagnosis of disease and improved preparations for allergen-specific immunotherapy. Grass pollen contains several different allergens, and although the group 3 allergens have been classified long ago, their structure and allergenicity have been poorly investigated.


OBJECTIVE
To characterize Phl p 3 from timothy grass pollen and compare it with Phl p 2 with respect to biochemical structure and allergenicity.


METHODS
Natural Phl p 2 and Phl p 3 were separated from a pollen extract by chromatography and characterized by 2D electrophoresis and protein sequencing. The complete sequences were determined by DNA cloning and detected in natural pollen extracts by mass spectrometry. Further comparisons of the allergens were made for IgE-binding and cross-reactivity, allergenicity was determined by basophil CD203c activation and skin prick test and 3D structures were compared by molecular modelling.


RESULTS
Phl p 3 reveals molecular masses of 10.958 and 10.973 kDa and pIs of 8.9 and 9.3, respectively, Phl p 2 a molecular mass of 10.816 kDa and a pI of 4.6. The sequence identity is 58%. In spite of these differences in the primary structures, both allergens reveal similar conformational structures, resulting in similar immunological and allergological moieties.


CONCLUSIONS
The group 3 and group 2 allergens are major allergens with similar 3D structures. Although they differ considerably in their protein sequences and their pIs, they show only a slightly higher immunological reactivity for Phl p 3 on the B-cell level (conformational epitopes). But distinct differences between the sequences may influence reactivity at the T cell level.
Petersen
Arnd
A
Molecular and Clinical Allergology, Research Center Borstel, Borstel, Germany. apetersen@fz-borstel.de
Suck
Roland
R
Lindner
Buko
B
Georgieva
Dessi
D
Ernst
Martin
M
Notbohm
Holger
H
Wicklein
Daniel
D
Cromwell
Oliver
O
Becker
Wolf-Meinhard
WM
D000485:Allergens / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D000595:Amino Acid Sequence; D000937:Antigen-Antibody Reactions; D052179:Antigens, Plant / Q000276:immunology / Q000302:isolation & purification*; D001483:Base Sequence; D001491:Basophils / Q000276:immunology; D015153:Blotting, Western / Q000379:methods; D002850:Chromatography, Gel / Q000379:methods; D002852:Chromatography, Ion Exchange / Q000379:methods; D003001:Cloning, Molecular; D003429:Cross Reactions; D015180:Electrophoresis, Gel, Two-Dimensional / Q000379:methods; D006801:Humans; D008969:Molecular Sequence Data; D031784:Phleum; D010727:Phosphoric Diester Hydrolases / Q000276:immunology; D010940:Plant Proteins / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification; D011058:Pollen; D017434:Protein Structure, Tertiary; D011755:Pyrophosphatases / Q000276:immunology; D017422:Sequence Analysis, DNA; D012882:Skin Tests
D000485:Allergens; D052179:Antigens, Plant; C427944:ENPP3 protein, human; C084984:PHLPII protein, Phleum pratense; C514376:Phl p 3 allergen, Phleum pratense; D010940:Plant Proteins; C090396:PHLPI protein, Phleum pratense; D010727:Phosphoric Diester Hydrolases; D011755:Pyrophosphatases