MTA-ELTE Protein Modelling Research Group and Laboratory of Structural Chemistry and Biology, Institute of Chemistry, Eötvös L. University, 1117 Budapest, Hungary
Institute of Enzymology, Research Centre for Natural Sciences, 1117 Budapest, Hungary
Kyou-Hoon Han
Gene Editing Research Center, Division of Convergent Biomedical Research, Korea Research Institute of Bioscience and Biotechnology, Daejeon 34141, Korea
Andras Perczel
MTA-ELTE Protein Modelling Research Group and Laboratory of Structural Chemistry and Biology, Institute of Chemistry, Eötvös L. University, 1117 Budapest, Hungary
Peter Tompa
Institute of Enzymology, Research Centre for Natural Sciences, 1117 Budapest, Hungary
Details of the functional mechanisms of intrinsically disordered proteins (IDPs) in living cells is an area not frequently investigated. Here, we dissect the molecular mechanism of action of an IDP in cells by detailed structural analyses based on an in-cell nuclear magnetic resonance experiment. We show that the ID stress protein (IDSP) A. thaliana Early Response to Dehydration (ERD14) is capable of protecting E. coli cells under heat stress. The overexpression of ERD14 increases the viability of E. coli cells from 38.9% to 73.9% following heat stress (50 °C × 15 min). We also provide evidence that the protection is mainly achieved by protecting the proteome of the cells. In-cell NMR experiments performed in E. coli cells show that the protective activity is associated with a largely disordered structural state with conserved, short sequence motifs (K- and H-segments), which transiently sample helical conformations in vitro and engage in partner binding in vivo. Other regions of the protein, such as its S segment and its regions linking and flanking the binding motifs, remain unbound and disordered in the cell. Our data suggest that the cellular function of ERD14 is compatible with its residual structural disorder in vivo.