Nonadaptive origin of novel protein associations

ARIEL FERNANDEZ

Viena

Congreso; Vienna Biocenter Ph D Symposium Nov. 18-19, 2010 - ORIGIN OF LIFE; 2010

Max F. Perutz Laboratories - Vienna Biocenter

Nonadaptive origin of novel protein associations: A large organism with a small population size is subject to the vagaries of random genetic drift and hence prone to acquire nonadaptive traits as a result of selection inefficiencies. These traits may be characterized at the molecular level by comparing the structures of proteins with common ancestry across species. Thus, as we examine orthologous proteins, we detect an accretion of mildly deleterious mutations in higher eukaryotes when compared with their unicellular counterparts. These substitutions may be regarded as neutral in the sense that they do not compromise the native tertiary structure or function, yet, strikingly, they introduce a latent selective advantage. The accumulation of these mutations promotes a destabilization of the protein structure which becomes more apparent as we consider species with small population, while a measure of the lost stability is recovered through protein-protein interactions. Thus, the nonadaptive traits shape an opportunity to acquire a selective advantage, manifested in the emergence of protein complexes endowed with allostery or other forms cooperative functionality. Hence, the emergence of novel protein-protein interactions, the hallmark of evolution in complex species, may well be rooted in completely nonadaptive processes.