cover illustration A population of thermophilic bacteria expressing the mesophilic adenylate kinase from Bacillus subtilis (55°C) were subjected to continuous evolution at increasing temperature (55-70°C). Substitution of glutamine-199 to arginine in the mesophilic enzyme expanded the organism's temperature niche by 9°C. We show that new ionic interactions facilitated by the mutant residue Arg-199 (pink) with Asn-196 and Asp-207 (purple) stabilize secondary structure elements in B. subtilis AK (purple) and shift the activity profile of the enzyme. The ability to identify functional intermediates during adaptation within a bacterial population allows the exploration of the adaptive landscape that constrains protein evolution and the identification of evolutionary strategies behind increased organismal fitness. For further details please see Couñago et al., pp. 19-27.
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