Molecular mechanisms governing stability of metallo-beta-lactamases during pathogenesis

GONZALEZ LJ; GONZÁLEZ MM; BAHR G; VILA AJ

San Miguel de Tucumán

Congreso; III Latin American Federation of Biophysical Societies (LAFeBS) - IX IberoAmerican Congress of Biophysics - XLV Reunion Anual SAB 2016; 2016

Sociedad Argentina de Biofísica

Carbapenems are last-resort -lactam antibiotics employed for the treatmentof multirresistant pathogens. In the last years, the number of carbapenemresistant bacteria has increased exponentially, principally bythe acquisition of zinc-dependent metallo--lactamases (MBLs) capableof inactivating most types of -lactam antibiotics. These enzymescarry out their activity in the bacterial periplasm, where they fold andbind Zn(II). During infection the host innate immune response withholdsnutrient metal ions from microbial pathogens by releasing metalchelatingproteins such as calprotectin, which limits the Zn(II) necessaryfor MBL activity.In previous work, we showed that sequestration of Zn(II) ions provokesa diminution in the periplasmic levels of MBLs, rendering the bacteriasusceptible to antibiotics. The nonmetallated forms generated underthese conditions are readily degraded.By means of biochemical, NMR and in vivo experiments, in the presentwork we aim to study how MBLs can evade the action of metal deprivationduring the host immune response. On one hand, we showthat membrane-anchoring of an unstable MBL, as is the case of theclinically relevant New Delhi metallo--lactamase (NDM-1), protectsthe enzyme from cellular degradation by localizing it in the bacterialouter membrane, in which the accessibility to proteases would be diminished.On the other hand, we demonstrate that BcII, a soluble MBL,circumvents metal limitation by exhibiting a stable and rigid scaffoldin the nonmetallated form, resilient to protein degradation. In conclusion,we unravel different evolutionary strategies adopted by MBLs toimprove bacterial resistance under challenging conditions encounteredduring pathogenesis.Acknowledgements: ANPCyT, NIH and CONICET.ReferencesGonzález LJ, Bahr G, Nakashige TG, Nolan EM, Bonomo RA, Vila AJ. Membrane anchoringstabilizes and favors secretion of New Delhi metallo--lactamase. Nat Chem Biol.2016; 12(7):516-22.