Metallo-β-lactamases: a Tug of War between Bacteria and the Inmune System for the available Zn(II)

BARH, GUILLERMO; ROSSI MA. AGUSTINA; TOMATIS PABLO E.; GIANNINI ESTEFANÍA; PALACIOS ANTONELA R.; CAROLINA LÓPEZ; JULIANA DELMONTI; GONZALEZ, LISANDRO J.; A. J. VILA

Encuentro; Protein Society Meeting, Boston, 2018; 2018

Metallo-β-lactamases(MBLs) are Zn(II)-dependent β-lactamases that constitute the latest resistancemechanism of pathogenic and opportunistic bacteria against carbapenems,considered as last resort drugs. Zn(II) binding is critical in the bacterialperiplasm, not only to activate these enzymes and provide resistance, but alsoto stabilize the protein scaffold. During infection, the immune system elicitsa response that scavenges the available Zn(II), impacting in the activity ofstability of these proteins, thus compromising bacterial survival. However, theactivity and stability of these proteins in vitro does not necessarilycorrelates with those in the periplasm. Thus, the whole picture must bedescribed by means of an integrated approach. We developed astrategy aimed to correlate the biochemical and biophysical features in purifiedenzymes with those in the bacterial periplasm, ultimately leading to theselected phenotype, i.e., resistanceto antibiotics. This strategy allows us to dissect the molecular features thatare tailored by accumulating mutations during evolution to endure the action ofthe immune system response. We have applied this approach to in vitro evolved protein in thelaboratory, as well as to natural allelic variants selected in clinicalstrains. This has allowed us to account for the epistatic interactions betweenmutations at a structural level. We have also studied thenatural evolutionary landscape of allelic variants of a clinically relevantlactamase (NDM), that has been shaped by Zn(II) deprivation conditions. Thus,natural NDM variants with enhanced Zn(II) binding affinity have been selected,overriding the most common evolutionary pressure acting on catalyticefficiency.