Protein function, in many cases, is highly related to its frustration status and hence intimately coupled to the dynamics and conformational equilibria of the protein. The environment surrounding proteins is critical for their dynamics and can dra-matically affect the conformational equilibria and subsequently activities of proteins. However, it is yet unclear how protein conformational equilibria are modulated by their crowded native environments. Here we revealed the immunity protein Im7 was less frustrated and shifted toward its ground state in OMVs than in the aqueous solution. Further experiments showed both macromolecular crowding and quinary interactions with the periplasmic components stabilized the ground state of Im7. Our studies highlight the key role of the OMVs environment played on protein conformational equilibria and subsequently conformation-related protein functions. Furthermore, the long-lasting NMR measurement time of proteins within OMVs underlies it could serve as a promising system to investigate protein structures and dynamics in situ via nuclear magnetic spectroscopy.
Methods and Materials