PoxA, YjeK, and Elongation Factor P Coordinately Modulate Virulence and Drug Resistance in Salmonella enterica

Abstract

SUMMARY We report an interaction between poxA, encoding a paralog of lysyl tRNA-synthetase, and the closely linked yjeK gene, encoding a putative 2,3-β-lysine aminomutase, that is critical for virulence and stress resistance in Salmonella enterica. Salmonella poxA and yjeK mutants share extensive phenotypic pleiotropy including attenuated virulence in mice, an increased ability to respire under nutrient limiting conditions, hypersusceptibility to a variety of diverse growth inhibitors and altered expression of multiple proteins including several encoded on the SPI-1 pathogenicity island. PoxA mediates post-translational modification of bacterial elongation factor P (EF-P), analogous to the modification of the eukaryotic EF-P homologue, eIF5A, with hypusine. The modification of EF-P is a mechanism of regulation whereby PoxA acts as an aminoacyl-tRNA synthetase that attaches an amino acid to a protein resembling tRNA rather than to a tRNA.

Distinct XPPX sequence motifs induce ribosome stalling, which is rescued by the translation elongation factor EF-P

“…In all cases, we were able to show that EF-P was able to efficiently relieve the translation stalling. Consistent with our findings was the identification of proteins containing PPP, PPG, or APP as being down-regulated when the genes encoding EF-P, YjeA, or YjeK were deleted in Salmonella (8,13). However, we did not observe any significant stalling in the absence of EF-P at non-diprolyl containing motifs, such as RME, YIR, PFF, YIRYIR, nor at the GSCGPG motif found in PoxB (Figs.…”

“…In bacteria, the translational arrest is relieved by the translation elongation factor P (EF-P), which binds to the stalled ribosomes and stimulates peptide bond formation (5,6). In Escherichia coli, EF-P is posttranslationally modified by YjeA, YjeK, and YfcM (EpmA, EpmB, and EpmC) (8)(9)(10) and the resulting lysinylation modification has been shown to be critical for the rescue activity of EF-P in vivo and in vitro (5,6). EF-P homologs exist in all archaea and eukaryotes, termed aIF-5A and eIF-5A, respectively (11).…”

(R)-β-Lysine-modified Elongation Factor P Functions in Translation Elongation

“…However, two recent studies also indicated that EF-P could act during elongation by facilitating the synthesis of proteins containing stretches of consecutive proline residues (5,6). EF-P is similar in size and shape to a tRNA and can be post-translationally modified by a lysyl-tRNA synthetase paralog, PoxA (7,8). In a reaction analogous to tRNA aminoacylation, PoxA activates (R)-␤-lysine and subsequently transfers it to a conserved residue (Lys-34) in EF-P (9).…”

“…In a reaction analogous to tRNA aminoacylation, PoxA activates (R)-␤-lysine and subsequently transfers it to a conserved residue (Lys-34) in EF-P (9). Attachment of a ␤-lysyl moiety is necessary for EF-P functionality both in vivo and in vitro (2,8). Recent mass spectroscopy analyses identified a second posttranslational modification of EF-P involving hydroxylation of the C4(␥) or C5(␦) of ␤-lysyl-Lys-34 by YfcM (10).…”

“…In S. enterica, disruptions of the genes encoding EF-P or the ␤-lysyl modification pathway result in a wide range of phenotypic changes including increased sensitivity to several antibiotics, loss of motility, attenuated virulence, and sensitivity to detergents and low osmolarity conditions (8). Many of these phenotypes are consistent with increased membrane permeability, suggesting a role for EF-P in regulating expression of outer membrane proteins, such as KdgM (3).…”