Fig. 3.

Microsporidian LeuRS is promiscuous toward near-cognate substrates. (A) The panel shows a fragment of the LeuRS synthetase crystal structure (Protein Data Bank ID code 1WKB) to illustrate high conservation of the leucine-binding pocket in the LeuRS aminoacylation site across eukaryotic species. Residues that directly bind leucine molecules are numbered according to Homo sapiens LeuRS numbering and are colored by conservation. Motif sequences (in orange) represent consensus sequences of the leucine-binding pocket. (B) Diagrams summarizing steady-state parameters for amino acid activation by microsporidian (E. cuniculi) and yeast (S. cerevisiae) LeuRS. This panel illustrates that microsporidian LeuRS can promiscuously activate near-cognate substrates norvaline (Nva), methionine (Met), valine (Val), and isoleucine (Ile), but not the noncognate substrate aspartate (Asp; used as a negative control).