Penicillin-binding proteins (PBPs) determine antibiotic action in Langmuir monolayers as nanoarchitectonics mimetic membranes of methicillin-resistant Staphylococcus aureus

The membrane of methicillin-resistant Staphylococcus aureus (MRSA) contains penicillin-binding proteins (PBPs) in the phospholipidic bilayer, with the protein PBP2a being linked with the resistance mechanism. In this work we confirm the role of PBP2a with molecular-level information obtained with Langmuir monolayers as cell membrane models. The MRSA cell membrane was mimicked with a mixed monolayer of dipalmitoyl phosphatidyl glycerol (DPPG) and cardiolipin (CL), also incorporating PBP2a. The surface pressure-area isotherms and the Brewster angle microscopy (BAM) images for these mixed monolayers were significantly affected by the antibiotic meropenem, which is PBP2a inhibitor. The meropenem effects were associated with the presence of PBP2a, as they were absent in the Langmuir monolayers without PBP2a. The relevance of PBP2a was confirmed with results where the antibiotic methicillin, known to be unsuitable to kill MRSA, had the same effects on mixed DPPG/CL and DPPG/CL-PBP2a monolayers since it prevented PBP2a from incorporating in the monolayer. The biological implication of the findings presented here is that a successful antibiotic against MRSA should be able to interact with PBP2a, but in the membrane.