title: Crystal structure of a hypoallergenic isoform of the major birch pollen allergen Bet v 1 and its likely biological function as a plant steroid carrier.
abstract: Bet v 1l is a naturally occurring hypoallergenic isoform of the major birch pollen allergen Bet v 1. The Bet v 1 protein belongs to the ubiquitous family of pathogenesis-related plant proteins (PR-10), which are produced in defense-response to various pathogens. Although the allergenic properties of PR-10 proteins have been extensively studied, their biological function in plants is not known. The crystal structure of Bet v 1l in complex with deoxycholate has been determined to a resolution of 1.9A using the method of molecular replacement. The structure reveals a large hydrophobic Y-shaped cavity that spans the protein and is partly occupied by two deoxycholate molecules which are bound in tandem and only partially exposed to solvent. This finding indicates that the hydrophobic cavity may have a role in facilitating the transfer of apolar ligands. The structural similarity of deoxycholate and brassinosteroids (BRs) ubiquitous plant steroid hormones, prompted the mass spectrometry (MS) study in order to examine whether BRs can bind to Bet v 1l. The MS analysis of a mixture of Bet v 1l and BRs revealed a specific non-covalent interaction of Bet v 1l with brassinolide and 24-epicastasterone. Together, our findings are consistent with a general plant-steroid carrier function for Bet v 1 and related PR-10 proteins. The role of BRs transport in PR-10 proteins may be of crucial importance in the plant defense response to pathological situations as well as in growth and development.
authors.affiliation: Department of Structural Biology, Biozentrum, University of Basel, CH-4056 Basel, Switzerland. zora.housley@unibas.ch
authors.forename: Zora
authors.initials: Z
authors.lastname: Marković-Housley
authors.forename: Massimo
authors.initials: M
authors.lastname: Degano
authors.forename: Doriano
authors.initials: D
authors.lastname: Lamba
authors.forename: Edda
authors.initials: E
authors.lastname: von Roepenack-Lahaye
authors.forename: Stephan
authors.initials: S
authors.lastname: Clemens
authors.forename: Markus
authors.initials: M
authors.lastname: Susani
authors.forename: Fátima
authors.initials: F
authors.lastname: Ferreira
authors.forename: Otto
authors.initials: O
authors.lastname: Scheiner
authors.forename: Heimo
authors.initials: H
authors.lastname: Breiteneder
mesh_terms: D000485:Allergens / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism*; D000595:Amino Acid Sequence; D052179:Antigens, Plant; D029662:Betula; D001665:Binding Sites; D060406:Brassinosteroids; D002777:Cholestanols / Q000378:metabolism; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D003840:Deoxycholic Acid / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010840:Phytosterols / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism*; D011058:Pollen / Q000737:chemistry* / Q000276:immunology; D011487:Protein Conformation; D020033:Protein Isoforms / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D021241:Spectrometry, Mass, Electrospray Ionization; D013260:Steroids, Heterocyclic / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D000485:Allergens; D052179:Antigens, Plant; D060406:Brassinosteroids; D002777:Cholestanols; D010840:Phytosterols; D010940:Plant Proteins; D020033:Protein Isoforms; D013260:Steroids, Heterocyclic; D003840:Deoxycholic Acid; C061312:Bet v 1 allergen, Betula; C083545:castasterone; C023623:brassinolide