Data for: Mini-alphaA-crystallin (MAAC) protects a client lens protein from catastrophic aggregation due to heat stress

A short peptide from human alphaA-crystallin (MAAC) retains chaperone activity, but the mechanism of chaperone-client interaction is unknown. In this study we investigate how the hydrophobicity of MAAC variants affects conformation and chaperone activity with human gammaS-crystallin (HgS). This data set comprise circular dichroism (CD) spectra and solution NMR experiments of WT MAAC and MAAC alanine variants (V3A, I4A, L6A, V8A, V18A) to observe differences in conformation and secondary structure. Dynamic light scattering (DLS) experiments show MAAC/HgS-WT chaperoning under thermal stress. The chaperone-client interaction is further observed with a series of 1H-15N-HSQC 2D-NMR MAAC titration experiments with HgS crystallin. MAAC-client interactions are further measured using variable-temperature and T2 relaxation NMR experiments for 300 uM 15N-HgS-WT (untreated) and MAAC-WT:HgS-WT (treated) samples when heated from 25-64 °C.

While MAAC variants are predominantly intrinsically disordered at dilute conditions, some beta-sheet characteristics are observed in WT MAAC at high concentrations. Structure characterization for selected MAAC variants were performed by TOCSY- and NOESY-2D-NMR experiments. Observations by NMR show that MAAC variants adopt a bent-characteristic in dilute conditions. When investigating MAAC-HgS crystallin chaperoning by DLS, we found that each hydrophobic residue was not interchangeable in terms of signficance. While the MAAC variants did not strongly interact with the client protein in mild temperatures, all but V18A suppressed catastrophic aggregation. Each variant also uniquely interacts with the client protein during the intermediate aggregation stage. When investigating chaperoning-client recognition, we found that only transient weak interactions in the form of subtle chemical shift perturbations are observed. Samples were individually prepared from stock solutions and allowed to incubate at each temperature point before data acquisition. The 1H-15N chemical shift perturbations describe changes in the electronic environment of the peptide amide backbone during thermal stress in the absence or presence of MAAC. Behavior of crosspeak movement provides insight into binding and conformational change. The appearance or disappearance of crosspeaks may signify large local conformational change due to strong binding.