All atom insights into the impact of crowded environments on protein stability by NMR spectroscopy

The high density of macromolecules affecting proteins due to volume exclusion has been discussed in theory but numerous in vivo experiments cannot be sufficiently understood taking only pure entropic stabilization into account. Here, we show that the thermodynamic stability of a beta barrel protein increases equally at all atomic levels comparing crowded environments with dilute conditions by applying multidimensional high-resolution NMR spectroscopy in a systematic manner. Different crowding agents evoke a pure stabilization cooperatively and do not disturb the surface or integrity of the protein fold. The here developed methodology provides a solid base that can be easily expanded to incorporate e.g. binding partners to recognize functional consequences of crowded conditions. Our results are relevant to research projects targeting soluble proteins in vivo as it can be anticipated that their thermodynamic stability increase comparably and has consequently to be taken into account to coherently understand intracellular processes.