Adaptive evolution: Eukaryotic enzyme's specificity shift to a bacterial substrate

Abstract

AbstractProlyl‐tRNA synthetase (ProRS), belonging to the family of aminoacyl‐tRNA synthetases responsible for pairing specific amino acids with their respective tRNAs, is categorized into two distinct types: the eukaryote/archaeon‐like type (E‐type) and the prokaryote‐like type (P‐type). Notably, these types are specific to their corresponding cognate tRNAs. In an intriguing paradox, Thermus thermophilus ProRS (TtProRS) aligns with the E‐type ProRS but selectively charges the P‐type tRNAPro, featuring the bacterium‐specific acceptor‐stem elements G72 and A73. This investigation reveals TtProRS's notable resilience to the inhibitor halofuginone, a synthetic derivative of febrifugine emulating Pro‐A76, resembling the characteristics of the P‐type ProRS. Furthermore, akin to the P‐type ProRS, TtProRS identifies its cognate tRNA through recognition of the acceptor‐stem elements G72/A73, along with the anticodon elements G35/G36. However, in contrast to the P‐type ProRS, which relies on a strictly conserved R residue within the bacterium‐like motif 2 loop for recognizing G72/A73, TtProRS achieves this through a non‐conserved sequence, RTR, within the otherwise non‐interacting eukaryote‐like motif 2 loop. This investigation sheds light on the adaptive capacity of a typically conserved housekeeping enzyme to accommodate a novel substrate.