Fig. 4: Binding interfaces between mtRNASer(UGA) and mSerRS.

a Overview of the mSerRS-mtRNASer(UGA) complex with regions enlarged in b, c, and d indicated. b Close-up view of the interactions between the acceptor arm of mtRNASer(UGA) (green) and the motif 2 loop (blue) at the entrance to the active site. c. Close-up view of the interactions of the T-stem (green) with the N-helix (wheat) and C-tail (blue) of mSerRS. d Close-up view of the interface between the T-loop (green) and the helical arm (wheat). Side chains of mSerRS are shown as sticks. Arg118, Arg139, and Arg143 are not resolved in the EM map and shown as their energetically most favorable rotamers. The electrostatic surface potential of mSerRS is shown transparently as a three-color gradient scheme from −5 to +5 kcal mol−1 e−1 (red, negative; white, neutral; blue, positive).