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![[Figure 3]](jb5072fig3mag.jpg)
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Figure 3
The ectodomains of the SRF6 and SRF7 proteins do not display high-affinity binding to the Arabidopsis BR receptors BRI1, BRL1 and BRL3. (a) Analytical size-exclusion chromatography of an equimolar mixture of BRL1 and SRF6. The absorbance trace at λ = 280 nm is shown in blue. Indicated are the void volume (v0) and the elution volumes for molecular-mass standards (Al, aldolase, 158 kDa; Ov, ovalbumin, 43 kDa; CA, carbonic anhydrase, 29 kDa). A Coomassie-stained SDS–PAGE of the peak fractions is shown alongside. (b) Isothermal titration calorimetry of SRF6 (in the syringe) versus BRL1 (in the cell). Shown are integrated heat peaks (upper panel) versus time and binding isotherms versus molar ratio of SRF6 ligand (lower panel). (c) Phylogenetic tree of the nine SRF family members annotated in the Arabidopsis genome. (d) Grating-coupled interferometry (GCI) binding kinetics of BRI1, BRL1 and BRL3 versus SRF6 and SRF7 in the presence of 100 nM brassinolide. The known BR co-receptor kinase SERK3 served as a positive control. Sensorgrams are shown with raw data in red and their respective fits in black. Binding kinetics were analysed by a 1:1 binding model. Tabular summaries of kinetic parameters are shown alongside (ka, association rate constant; kd, dissociation rate constant; KD, dissociation constant; n.d., no detectable binding). |
![[Figure 3]](jb5072fig3.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
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