Figure 6. CHL1ID/Hsc70/αSGT and CHL1ID/CSP chaperone complexes dissolve aggregates of SNAP25 and VAMP2, respectively.

A – CD spectra of native and heat-treated non-native SNAP25 and VAMP2. Exposure of the proteins to 42°C for 10 min did not affect the secondary structure of the proteins, as revealed by almost identical CD spectra. A minor shift of the characteristic minimum towards 200 nm might indicate a slight increase in their random coil structure content. B - Distribution of the radii of the protein complexes as measured by DLS. Data from 22 consecutive DLS measurements are shown with signal intensities displayed in pseudocolor. Heat exposure results in aggregation of SNAP25 and VAMP2 (solid and dashed lines mark the size of particles formed by proteins in native and non-native conformations, respectively). CHL1ID, Hsc70 and αSGT form a complex, which is larger than the complex formed by CHL1ID and CSP. The sizes of these complexes are marked by dotted lines (the same data are shown in two columns for reference). Note, that SNAP25 and VAMP2 aggregates are dispersed in the presence of ATP by CHL1ID/Hsc70/αSGT and CHL1ID/CSP, respectively. Protein aggregates are not dispersed in the absence of nucleotides or in the presence of ADP. Under these conditions, the aggregates and CHL1ID/Hsc70/αSGT complex are seen as assemblies of two distinct sizes, with the smaller CHL1ID/CSP complex being obscured by the larger aggregates, because the scattering intensity is proportional to the particle radius in the power of 3 [52]. SNAP25 aggregates are not dispersed by CHL1ID/CSP, and VAMP2 aggregates are not dispersed by CHL1ID/Hsc70/αSGT.