In Vivo Cross-Linking MS Reveals Conservation in OmpA Linkage to Different Classes of β-Lactamase Enzymes

Molecular interactions between two different classes of beta-lactamase enzymes and outer membrane protein A (OmpA) were studied by in vivo chemical cross-linking of a multi-drug-resistant strain of Acinetobacter baumannii AB5075. Class A beta-lactamase blaGES-11 and Class D beta-lactamase Oxa23, responsible for hydrolysis of different types of beta-lactam antibiotics, were found to be cross-linked to similar lysine sites of the periplasmic domain of outer membrane protein OmpA, despite low sequence homology between the two enzymes. The findings from in vivo XL-MS suggest that the interacting surfaces between both beta-lactamase enzymes and OmpA are conserved during molecular evolution, and the OmpA C-terminus domain serves an important function of anchoring different types of beta-lactamase enzymes in the periplasmic space.