Specific protein-membrane interactions promote the export of metallo-β-lactamases via outer membrane vesicles

Outer membrane vesicles (OMVs) act as carriers of resistance determinants such as metallo-{beta}-lactamases. The metallo-{beta}-lactamase NDM-1 is present in OMVs produced by Gram-negative bacteria since it is a lipidated, membrane-anchored protein. The soluble domain of NDM-1 also forms electrostatic interactions with the membrane. Herein, we show that these interactions promote its export into OMVs produced by Escherichia coli. We report that favorable electrostatic protein-membrane interactions are also at work in the soluble enzyme IMP-1, while being absent in VIM-2. These interactions correlate with an enhanced secretion into OMVs of IMP-1 compared to VIM-2. Disruption of these interactions in NDM-1 and IMP-1 impairs export into vesicles, confirming their role in defining the protein cargo in OMVs. These results also indicate that export of metallo-{beta}-lactamases into vesicles in their active form is a common phenomenon that involves cargo selection based on molecular features.