Stall no more at polyproline stretches with the translation elongation factors EF‐P and IF‐5A

Abstract

SummarySynthesis of polyproline proteins leads to translation arrest. To overcome this ribosome stalling effect, bacteria depend on a specialized translation elongation factor P (EF-P), being orthologous and functionally identical to eukaryotic/archaeal elongation factor e/aIF-5A (recently renamed 'EF5'). EF-P binds to the stalled ribosome between the peptidyl-tRNA binding and tRNA-exiting sites, and stimulates peptidyltransferase activity, thus allowing translation to resume. In their active form, both EF-P and e/aIF-5A are post-translationally modified at a positively charged residue, which protrudes toward the peptidyltransferase center when bound to the ribosome. While archaeal and eukaryotic IF-5A strictly depend on (deoxy-) hypusination (hypusinylation) of a conserved lysine, bacteria have evolved diverse analogous modification strategies to activate EF-P. In Escherichia coli and Salmonella enterica a lysine is extended by β-lysinylation and subsequently hydroxylated, whereas in Pseudomonas aeruginosa and Shewanella oneidensis an arginine in the equivalent position is rhamnosylated. Inactivation of EF-P, or the corresponding modification systems, reduces not only bacterial fitness, but also impairs virulence. Here, we review the function of EF-P and IF-5A and their unusual posttranslational protein modifications.

eIF5A facilitates translation termination globally and promotes the elongation of many non polyproline-specific tripeptide sequences

“…In bacteria, ribosome profiling experiments have shown that stalling at PP dipeptides is enhanced by the presence of specific amino acids upstream and/or downstream of the motif. Remarkably, the pausing motifs that we identified in yeast contained all the tripeptides that have been previously described to cause strong stalling in bacteria (PPP, PPG, PPQ, PPR, PPD, PPW, PPN, DPP, EPP, GPP and APP) ((31–35) and reviewed in (54)).…”

Role of mRNA structure in the control of protein folding

“…Ribosome stalling caused by the ‘arrest peptides’ that block the ribosomal exit channel affects the structure of the mRNA, resulting in specific biological effects including regulation of protein production, maturation or localization (19). Notably, it has been shown that to overcome stalling at polyproline sequences, the ribosome requires a specific translation elongation factor (17). The availability of tRNAs also can affect the rate of elongation of nascent polypeptide chains (20).…”

Novel Antibiotic Resistance Determinants from Agricultural Soil Exposed to Antibiotics Widely Used in Human Medicine and Animal Farming

“…Sequences containing consecutive proline residues (especially with three or more) can trigger significant stalling of the bacterial ribosome, which is effectively rescued by the translation elongation factor EF-P (40-43). The likelihood of a nascent peptide becoming arrested at its diproline motif is determined by the identity of residues flanking the proline pair (41,(44)(45)(46). In contrast to strong stalling sequences (e.g., PPP), PPR and RPP motifs (where R ϭ Arg) confer weak stalling activity, as their translation has little reliance on the activity of EF-P (41,45).…”

“…The likelihood of a nascent peptide becoming arrested at its diproline motif is determined by the identity of residues flanking the proline pair (41,(44)(45)(46). In contrast to strong stalling sequences (e.g., PPP), PPR and RPP motifs (where R ϭ Arg) confer weak stalling activity, as their translation has little reliance on the activity of EF-P (41,45). Furthermore, in vivo PPK (where K ϭ Lys) is translationally arrested only when preceded by an acidic residue (44).…”