Crystal Structures of Weissella viridescens FemX and Its Complex with UDP-MurNAc-Pentapeptide: Insights into FemABX Family Substrates Recognition

Abstract

Members of the FemABX protein family are novel therapeutic targets, as they are involved in the synthesis of the bacterial cell wall. They catalyze the addition of amino acid(s) on the peptidoglycan precursor using aminoacylated tRNA as a substrate. We report here the high-resolution structure of Weissella viridescens L-alanine transferase FemX and its complex with the UDP-MurNAc-pentapeptide. This is the first structure example of a FemABX family member that does not possess a coiled-coil domain. FemX consists of two structurally equivalent domains, separated by a cleft containing the binding site of the UDP-MurNAc-pentapeptide and a long channel that traverses one of the two domains. Our structural studies bring new insights into the evolution of the FemABX and the related GNAT superfamilies, shed light on the recognition site of the aminoacylated tRNA in Fem proteins, and allowed manual docking of the acceptor end of the alanyl-tRNAAla.

Structures of two bacterial resistance factors mediating tRNA-dependent aminoacylation of phosphatidylglycerol with lysine or alanine

“…FemX catalyzes the transfer of L-Ala to the side chain of the e-amino group of L-Lys of the peptidoglycan precursor UDPMurNAc-pentapeptide (20). The core of the FemX protein also is composed of two GNAT domains that are related by pseudotwofold symmetry (rmsd for internal superposition, 2.0 Å) (21). Structural domains 1 and 2 are separated by an extended cleft of 20 Å that is 15 Å deep to accommodate both the UDP-MurNAcpentapeptide on GNAT domain 1 and the unpaired CCA acceptor arm of the charged tRNA on GNAT domain 2 (20).…”

The determination of tRNALeu recognition nucleotides for Escherichia coli L/F transferase

“…A group of aminoacyl-tRNA protein transferases involved in peptidoglycan biosynthesis have a similar structural fold, but are dissimilar in substrate specificity or function, to L/F transferase (Benson et al 2002;Biarrotte-Sorin et al 2004;Rai et al 2006;Dong et al 2007). Factors essential for methicillin resistance (Fem) transferase X from Weissella viridescens (FemX Wv ) transfers L -Ala from L -Ala-tRNA Ala to UDPMurNAc-pentapeptide (Maillard et al 2005).…”

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

“…Thus, Tyr42 is located within hydrogenbonding distance to Tyr120 and Glu156. It seems that Tyr120 and Glu156 are structurally similar to the critical residues for UDP-MPP binding in the FemX complex structure (Hegde and Shrader 2001;Biarrotte-Sorin et al 2004). The other completely conserved residues, Asp186 and Gln188, are located at the end of b5, and Asp186 is positioned within hydrogen-bonding distance to Glu156 via two water molecules (Fig.…”

“…The FemX UDP-MurNAc-pentapeptide (UDP-MPP):L-alanine transferase from Weissella viridescens is a cell-wall peptidoglycan biosynthesis-related protein, which consists of two domains, and it has a long substrate binding cleft (Hegde and Shrader 2001;Biarrotte-Sorin et al 2004). Based on their structural and peptidyltransferase reaction similarities, we superimposed the L/F-transferase and FemX structures.…”