Dissection of the in vivo interplay of molecular features determining protein evolution

MARÍA-ROCÍO MEINI; GONZALEZ, L; TOMATIS, P E; A. J. VILA

Puerto Varas

Congreso; XII PABMB Congress; 2013

Protein evolution can be described as a random walk on a sequence space where mutations are fixed based on their impact on the organismal fitness. Fitness is a measure of the host organism´s ability to reproduce faster at the conditions imposed by the environment. Two of the major challenges in the field of protein evolution are to understand: (1) how the structural, functional and biophysical features of proteins determine molecular evolution, and (2) how mutations accumulate and impact in these molecular features.The order in which mutations appear is not trivial, since the effect of each mutation depends on the genetic background, a phenomenon known as epitasis.   We have analyzed the molecular features evinced by the accumulation of mutations in the evolutionary pathways of a Metallo-β-lactamase, a Zn(II)-dependent enzyme able to provide antibiotic resistance to pathogenic and opportunistic bacteria. We have been able to assess the impact of four different mutations and their combinations in the protein stability and function in the periplasmic space. This approach allows us to fill the gap between the biochemical and biophysical features determined in vitro in purified proteins, and the resistance conferred to bacteria, which ultimately represents organismal fitness. We also found that epistatic interactions in the evolutionary pathways can be accounted for by only three molecular properties evaluated in periplasma: catalytic efficiency, protein stability and enzyme activation by binding of the essential Zn(II) cofactor in vivo.