Conformational plasticity of the intrinsically disordered protein ASR1 modulates its function as a drought stress-responsive gene
Fig 3
Zn2+ effects on ASR1 functions.
A). CD spectrum at 25°C of ASR1 (2 μM) with oligoC (15 μM) full line corresponds to the oligo-protein mixture and dash line represents the algebraic sum of the individual spectrum; inset: spectra of the ASR1 (full line) and oligoC (dash line) alone. B) Fluorescence anisotropy titration. Binding experiments were performed by adding recombinant ASR1 protein to a fixed amount of FITC dsDNA (250 nM). Measurements performed in buffer H with Zn2+ (100 μM): FITC-oligoC (full circles) and FITC-oligoS (full triangles) and without Zn2+: FITC-oligoC (empty circles). Lines correspond to the best fit to the Eq 5 and error bars correspond to the standard errors of two individual experiments. Inset: Fluorescence intensity change as a function of ASR1 concentration performed on nearly saturating conditions (FITC-oligoC: 1250 nM). The arrow indicates the 1:1 stoichiometry. C and D) CS (100 nM) was incubated at 43°C at the indicated ASR1:CS ratios in absence (dashed line) or presence (full line) of 50 μM Zn 2+. +Trehalose indicates the addition of 100 mM trehalose. Plots show light scattering (OD360nm) relative to the highest value obtained on the CS alone sample. CS alone and ASR1 alone were used as controls. Mean values of at least 3 measurements.