ANCESTRAL RECONSTRUCTION OF A β-LACTAMASE AND COMPARISON WITH ITS EXTANT PROTEINS

The β-lactamases are proteins of bacterial origin that are characterized by hydrolyzing antibiotics β-lactams, conferring microbial resistance against them. They are a heterogeneous family of proteins very relevant from a health point of view due to the ease they present to acquire resistance to new drugs due to their high capacity for evolution. The in vitro evolution of these proteins has served not only to develop their characterization and improve their knowledge, but as a new line of research that allows to predictively identify residues involved in the acquisition of antibiotic resistance. At the same time, the method of ancestral protein reconstruction has been revealed as a novel and useful tool to understand the evolution of β-lactamases and understand some of their characteristics such as their promiscuity. In this work, a study of ancestral β-lactamases reconstructed from the phylogeny of existing class A β-lactamases has been carried out. Of the four ancestral proteins studied, one has been obtained that is functional and has compared its hydrolytic activity with that of four of its current counterparts against eight β-lactam drugs. This ancestral protein has been shown to have a more generalistic antibiotic activity than any of the current proteins studied. In addition, the active ancestral protein showed more resistance to one of the drugs used than the rest of β-lactamases existing. Finally these results have been discussed and from them it is argued why reconstructed ancestral sequences can be a very attractive starting point when it comes to direct evolution of proteins for obtaining proteins of biotechnological interest.