Different conformational changes of sRNA Pab21 and Pab91 are associated with the sequential binding of the sRNP proteins.

<p>(<b>A</b>) CD spectra of sRNAs Pab21 (red) and Pab91 (blue) scanned in the range 240 to 320 nm. (<b>B</b>) CD spectra of sRNA Pab21 obtained when protein aCBF5 and the sRNA are present in two separate cell compartments (dark blue) or after mixing the two compartments (green). Spectra obtained following sequential addition of proteins to the aCBF5–Pab21 complex: aNOP10 (magenta) added first and then L7Ae (light blue). (<b>C</b>) Same experiment as in panel B but with Pab91. (<b>D</b>) CD spectra of sRNA Pab21 obtained with the sRNA and L7Ae in separate compartments (dark purple) and after mixing (purple). (<b>E</b>) Quantification of the decrease in the peak amplitude of the specific RNA positive signal at the λ_max wavelength, generated exclusively by addition of L7Ae to different aCBF5–aNOP10–sRNA complexes. The resulting δ(Δε) values are displayed as a histogram for each complex. sRNP assembly was achieved by incubation of aCBF5–Pab21 with the mutant of L7Ae (H70A/L74A/E77A designated HLE) or the mutant of aNOP10 (Y41A/Y44A designated Y).