The crystal structure of leucyl/phenylalanyl‐tRNA‐protein transferase from Escherichia coli

Leucyl/phenylalanyl‐tRNA‐protein transferase (L/F‐transferase) is an N‐end rule pathway enzyme, which catalyzes the transfer of Leu and Phe from aminoacyl‐tRNAs to exposed N‐terminal Arg or Lys residues of acceptor proteins. Here, we report the 1.6 Å resolution crystal structure of L/F‐transferase (JW0868) from Escherichia coli , the first three‐dimensional structure of an L/F‐transferase. The L/F‐transferase adopts a monomeric structure consisting of two domains that form a bilobate molecule. The N‐terminal domain forms a small lobe with a novel fold. The large C‐terminal domain has a highly conserved fold, which is observed in the GCN5‐related N‐acetyltransferase (GNAT) family. Most of the conserved residues of L/F‐transferase reside in the central cavity, which exists at the interface between the N‐terminal and C‐terminal domains. A comparison of the structures of L/F‐transferase and the bacterial peptidoglycan synthase FemX, indicated a structural homology in the C‐terminal domain, and a similar domain interface region. Although the peptidyltransferase function is shared between the two proteins, the enzymatic mechanism would differ. The conserved residues in the central cavity of L/F‐transferase suggest that this region is important for the enzyme catalysis.