Creation of an Amino Acid Network of Structurally Coupled Residues in the Directed Evolution of a Thermostable Enzyme

摘要

The traditional view of enzymes as being composed of dense networks of amino acids that interact locally is widely accepted, yet it is incomplete. Recent research has shown that protein function is also influenced substantially by nonlocal, long-range interactions between residues in a communicating amino acid network. It is not a trivial task to identify the precise nature of this phenomenon on a molecular level, but it has in fact been postulated in some enzyme-catalyzed processes, in allosteric regulation of proteins, and in information transfer between distal functional surfaces on signaling proteins. Distal effects have been noted in some directed-evolution studies, although their role in putative amino acid networks has not been the focus of interest. Efficiency in laboratory evolution may well depend on the occurrence of such interacting residues in an amino acid network, because this would maximize the probability of cooperative effects. Can laboratory evolution create new amino acid networks by forming communicating links between distal residues? Here we show that this is indeed possible, specifically in the thermostabilization of an enzyme.