Periplasmic protein quality control at atomic level in live cells

The periplasm of gram-negative bacteria facilitates critical functions, includingnutrient uptake, cell wall metabolism, antibiotic resistance, and virulence.Efficient quality control of proteins involved in these processes is crucial forbacterial fitness and survival. The limited size of the periplasm has hinderedhigh-resolution mechanistic investigations of complex processes within thiscompartment. Using in-cell NMR spectroscopy, we dissect the mechanism ofperiplasmic quality control of the metallo-β-lactamase NDM-1 under condi-tions of zinc starvation, which destabilizes its native structure promoting itsdegradation. We show that the protease Prc targets membrane-bound NDM-1at specific residues and secondary structure motifs, while DegP processespeptides generated by Prc. This approach discloses the concerted mechanismof these proteases at atomic resolution in the periplasm of live cells.