IBR   13079
INSTITUTO DE BIOLOGIA MOLECULAR Y CELULAR DE ROSARIO
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Insights into Enzyme Evolution Revealed by Lactamases
Autor/es:
MARÍA ROCÍO MEINI; PABLO E. TOMATIS; ALEJANDRO J. VILA
Lugar:
Quilmes
Reunión:
Congreso; A2B2C 2010 1er Congreso Argentino de Bioinformática y Biología Computacional; 2010
Institución organizadora:
Asociación Argentina de Bioinformática y Biología Computacional
Resumen:
Directed
Molecular Evolution (DME) strategies are currently exploited to generate stable
proteins, improve the catalytic efficiency, shape the substrate specificity of
enzymes, or design new activities. We have shown that DME on the metallo-beta-lactamase
BcII from B. cereus gives rise to a variant with enhanced catalytic and
resistance traits conferred by four mutations. Two of them, G262S and N70S,
located under the active site floor, show a strong sign epistasis for fitness.
G262S increases the enzyme catalytic efficiency and N70S, the flexibility of
the active site. The other two, V112A and L250S, are located far away from the
active site, and their influence on the enzyme function is not so obvious. We
analyzed how these mutations are able to enhance fitness and we identified the
possible pathways that could lead to the acquisition of larger levels of
resistance. Interestingly, only one third of the 24 possible evolutionary
pathways are accessible. This restriction is mainly due to the fact that
mutation G262S acts as a bottleneck, providing a more evolvable genetic
background than wt BcII. However, the increase in the enzyme activity was not
enough to explain its enhanced capacity to confer resistance. We have found
that V112A acts as a stabilizing mutation, therefore, we can conclude that
stability is another contributing factor to the enzyme fitness.