Figure 3: Hsp70-binding sites of Sti1.
From: Hsp90 regulates the dynamics of its cochaperone Sti1 and the transfer of Hsp70 between modules
(a) SAXS data showing a comparison of the experimental radial density distributions of Hsp70 at increasing stoichiometric ratios of wild-type Sti1 as indicated. (b) Affinities of Sti1 variants towards yHsp70 determined by surface plasmon resonance spectroscopy with an Hsp70-coupled chip, normalized to wild-type Sti1 levels. Error bars indicate fitting error. (c–e) Formation of ternary Hsp90–Sti1–Hsp70 complexes using (c) wild-type Sti1, (d) Sti1 N39A and (e) Sti1 TPR2A-TPR2B. The 0.5 μM fluorescein-labelled yHsp70 and 3 μM yHsp90 were incubated with 0.5 (black), 1 (orange), 2 (blue) and 4 μM (cyan) Sti1 variant in 10 mM potassium phosphate at pH 7.5. Analytical ultracentrifugation was performed at 20 °C and 42 000 r.p.m. Sedimentation profiles were converted into dc/dt plots using standard procedures46 and fitted with bi-Gaussian functions. For clarity, only fits are shown, s.e. values were below 1%. As orientation, the lines indicate observed sedimentation coefficients (Hsp70* alone 4.2 S, left, binary complexes of Hsp70* with Sti1 5.6 S and ternary complexes of Hsp70* with Sti1 and Hsp90 8–10 S) from previous studies.
