Lupinus luteus Pathogenesis-Related Protein as a Reservoir for Cytokinin

The RNA Hydrolysis and the Cytokinin Binding Activities of PR-10 Proteins Are Differently Performed by Two Isoforms of the Pru p 1 Peach Major Allergen and Are Possibly Functionally Related

“…In this regard, it is interesting to note that, while all PR-10 proteins contain a highly conserved and stable b-sheet, they show structural variability in the a-helical content. In particular, the conformation of helix a3 determines the accessibility, the size, and the shape of the hydrophobic cavity that holds zeatin or other ligands (Biesiadka et al, 2002;Pasternak et al, 2006;Fernandes et al, 2008Fernandes et al, , 2009). …”

“…PR-10 proteins have been considered a multifunctional protein family, encompassing different functional subfamilies that share homology in tertiary structure in spite of low sequence similarity. The specific interaction of several PR-10 proteins with CKs has been so far associated with a function of storage and transport of these plant hormones (Fernandes et al, 2008) as well as with a possible regulatory role in RNase activity, CK metabolism, and stress defense (Srivastava et al, 2007). The calorimetric titration experiments described in this study showed that Pru p 1.01 binds one zeatin molecule per protein monomer with a dissociation constant of approximately 10 mM, while Pru p 1.06D does not show any binding capability under the same experimental conditions.…”

“…Indeed, the available crystal structures of PR-10 proteins in complex with zeatin show that the ligand-protein interaction is not structurally conserved: VrCSBP was crystallized with one or two zeatin molecules in the binding pocket (Pasternak et al, 2006). Conversely, the lupin LlPR-10.2B crystal structure shows three zeatin molecules bound inside the pocket (Fernandes et al, 2008). The orientation of the zeatin molecule bound deeper in the pocket is different in the two structures, indicating that proteins with the same scaffold but located in distant regions of the phylogenetic tree, and belonging to different taxonomic orders, have developed the capability of bind a different amount of zeatin molecules in different ways (Fernandes et al, 2008).…”

“…This is revealed by the structures of a number of PR-10 proteins obtained by NMR and x-ray crystallography, such as Bet v 1 from birch (Betula spp. ; Gajhede et al, 1996;Markovic-Housley et al, 2003), four isoforms of LlPR10 from yellow lupin (Lupinus luteus; Biesiadka et al, 2002;Pasternak et al, 2005;Fernandes et al, 2008), VrCSBP (cytokininspecific binding protein) from mung bean (Vigna radiata; Pasternak et al, 2006), Pru av 1 from cherry (Prunus avium; Neudecker et al, 2001), and Ap g 1 from celery (Apium graveolens; Schirmer et al, 2005).…”

“…Additional roles of PR-10 proteins could be related to their capability to bind hydrophobic ligands, such as fatty acids, flavonoids, and steroids (Neudecker et al, 2001;Mogensen et al, 2002;Koistinen et al, 2005). PR-10 proteins are also capable of binding plant hormones, such as cytokinins (CKs; Fujimoto et al, 1998;Pasternak et al, 2006;Fernandes et al, 2008). CKs are signal elements that regulate plant growth and development, but which are also recently emerging as important components of the plant defense strategy repertoire (Chung et al, 2008).…”