Journal of Physical Chemistry B, Vol.124, No.14, 2747-2759, 2020
Group 3 LEA Protein Model Peptides Suppress Heat-Induced Lysozyme Aggregation. Elucidation of the Underlying Mechanism Using Coarse-Grained Molecular Simulations
We investigated experimentally whether a short peptide, PvLEA-22, which consists of two tandem repeats of an 11-mer motif of Group 3 late embryogenesis abundant proteins, has a chaperone-like function for denatured proteins. Lysozyme was selected as a target protein. Turbidity measurements indicated that the peptide suppresses the heat-induced aggregation of lysozyme when added at a molar ratio of PvLEA-22/lysozyme >40. Circular dichroism and differential scanning calorimetry measurements confirmed that the lysozyme was denatured on heating but spontaneously refolded on subsequent cooling in the presence of the peptide. As a result, up to 80% of the native catalytic activity of lysozyme was preserved. Similar chaperone-like activity was also observed for a peptide with the same amino acid composition as PvLEA-22 but whose sequence is scrambled. To elucidate the underlying mechanism of the chaperone function of these peptides, we performed coarse-grained molecular dynamics simulations. This revealed that a denatured lysozyme molecule is shielded by several peptide molecules in aqueous solution, which acts as a physical barrier, reducing the opportunities for collision between denatured proteins. An important finding was that a peptide bound to the denatured protein is very rapidly replaced by another; due to such rapid exchange, peptide-protein contact time is very short, that is, on the order of similar to 200 ns. Therefore, the peptide does not constrain the behavior of the denatured protein, which can refold freely.