The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
The Pseudomonas putida KT2440 gene earP (UniProt Q88LS1, locus PP_1857) encodes EarP, a cytosolic protein-arginine rhamnosyltransferase (glycosyltransferase family GT-B / “GT-B–type” fold) that post-translationally activates translation elongation factor P (EF-P) by transferring rhamnose from dTDP-β-L-rhamnose (TDP-Rha) to EF-P Arg32 (R32), generating rhamnosyl-arginine on EF-P. This modification is required for EF-P activity in a subset of bacteria (including pseudomonads) and is linked to polyproline-translation rescue, bacterial fitness, and (in pathogenic pseudomonads) virulence. (krafczyk2017structuralbasisfor pages 2-3, krafczyk2017structuralbasisfor pages 1-2, lassak2015argininerhamnosylationasnew pages 10-15)
All primary sources used here explicitly treat EarP as the EF-P Arg32 rhamnosyltransferase and include work directly on EarP from P. putida KT2440 (e.g., crystal structure and donor binding). This matches the UniProt record provided (Q88LS1; RecName “Protein-arginine rhamnosyltransferase”; gene name earP; organism P. putida KT2440). No alternative “earP” (unrelated function) was used. (krafczyk2017structuralbasisfor pages 2-3, krafczyk2017structuralbasisfor pages 1-2)
Bacterial translation can stall at polyproline motifs (consecutive prolines), and EF-P is a specialized translation factor that rescues these stalls. In bacteria that use the EarP system, EF-P requires post-translational modification of a conserved residue (Arg32) to become fully active. Structural/functional models place activated EF-P at the ribosome (between E and P sites) where the modified residue helps stabilize the P-site prolyl-tRNA geometry to promote peptide bond formation. (krafczyk2017structuralbasisfor pages 2-3)
EarP performs protein N-glycosylation on arginine, specifically transferring a rhamnose to the guanidino group of EF-P Arg32. In discovery work, the modified EF-P peptides show a +146.058 Da mass shift consistent with rhamnose − H2O (C6H10O4). (lassak2015argininerhamnosylationasnew pages 10-15, lassak2015argininerhamnosylationasnew pages 1-10)
EarP uses dTDP-L-rhamnose as its sugar donor. In vitro reconstitution experiments required both purified EarP and dTDP-L-rhamnose to generate rhamnosylated EF-P peptides. Cellular pools of TDP-β-L-rhamnose are reported to be in the high micromolar range in E. coli, P. putida, and P. aeruginosa (measured using antibody-enabled assays). (lassak2015argininerhamnosylationasnew pages 10-15, krafczyk2018exceptionallysweetstudieson pages 91-94, krafczyk2018exceptionallysweetstudiesonb pages 91-94)
Enzyme: EarP (EC 2.4.1.-; protein-arginine rhamnosyltransferase)
Reaction (functional annotation):
dTDP-β-L-rhamnose + EF-P(Arg32) → dTDP + EF-P(Arg32–Rha)
EarP is described as an inverting glycosyltransferase, consistent with a single-displacement SN2-like transfer mechanism producing α-rhamnosyl-arginine on EF-P. (krafczyk2017structuralbasisfor pages 2-3, krafczyk2017structuralbasisfor pages 11-12, krafczyk2018exceptionallysweetstudieson pages 91-94)
The crystal structure of EarP from P. putida KT2440 reveals a GT-B fold composed of two opposing Rossmann-like domains forming an interdomain cleft. In the donor-bound structure, TDP-Rha sits in a highly conserved pocket located in the C-terminal domain. (krafczyk2017structuralbasisfor pages 2-3, krafczyk2017structuralbasisfor pages 1-2)
A reported structure resolution is 2.3 Å for EarP bound to TDP-Rha (PDB referenced in the study). (krafczyk2017structuralbasisfor pages 2-3)
Mechanistic models and mutational evidence implicate:
* D13, D17, E273 as invariant acidic residues proposed to activate the arginine acceptor; D17 and E273 have been proposed as a catalytic dyad. (krafczyk2018exceptionallysweetstudieson pages 45-46, krafczyk2017structuralbasisfor pages 11-12)
* F252, F258 aromatic residues that stack with the thymine/ribose portions of the nucleotide donor, stabilizing donor positioning. (krafczyk2017structuralbasisfor pages 11-12)
* R271 (invariant) implicated in stabilizing the leaving group/product; mutation R271A strongly impairs function. (krafczyk2017structuralbasisfor pages 11-12, krafczyk2018exceptionallysweetstudieson pages 45-46)
NMR-based observations support that EarP can bind donor or acceptor independently (i.e., binding is not strictly ordered), fitting a multi-step model (unbound → donor-bound → catalytic state → release). (krafczyk2018exceptionallysweetstudieson pages 45-46)
EarP activity depends on intracellular availability of TDP-Rha, produced by the canonical RmlA–RmlD pathway. In P. putida KT2440, detailed genetic assignments for the late steps include:
* PP_1782 (RmlC1) and PP_0265 (RmlC2): paralogous epimerases catalyzing the epimerization step leading toward TDP-L-rhamnose.
* PP_1784 (RmlD): reductase catalyzing the final reduction to TDP-L-rhamnose.
These assignments were supported by complementation and EF-P rhamnosylation readouts using anti-ArgRha immunodetection. (koller2021twormlchomologs pages 2-4, koller2021functionanddistribution pages 35-38, koller2021twormlchomologs pages 1-2)
Direct subcellular fractionation/localization experiments were not identified in the retrieved evidence. However, based on substrate identity (soluble EF-P) and functional models placing activated EF-P on cytosolic ribosomes, EarP’s site of action is best supported as cytosolic (intracellular), acting on EF-P prior to (or in equilibrium with) EF-P engagement with ribosomes. (krafczyk2017structuralbasisfor pages 2-3)
A genetic/functional link between TDP-Rha supply and EF-P activation is supported by heterologous reporter experiments: when P. putida efp/earP is expressed in an E. coli Δefp strain, loss of a key TDP-Rha biosynthesis step (ΔrmlC) results in approximately 2-fold slower growth compared with the intact pathway background, demonstrating donor-supply limitation has a strong functional effect on the EF-P/EarP system. (koller2021twormlchomologs pages 2-4)
Additionally, an unbiased genomic library screen (~430,000 clones; ~350× genome coverage) identified the relevant P. putida rmlC genes (PP_1782 and PP_0265) by selection for restored EF-P/EarP-dependent growth phenotypes, supporting pathway robustness and redundancy at the rmlC step. (koller2021twormlchomologs pages 2-4, koller2021functionanddistribution pages 35-38)
In the pathogen Pseudomonas aeruginosa, loss of earP abolishes pathogenicity/virulence-associated outputs, and EF-P/EarP are implicated in production of quorum-sensing-dependent virulence factors (e.g., rhamnolipids and pyocyanin). These findings motivate EarP as a potential anti-virulence/antimicrobial target and underlie statements that EarP structural information provides a basis for inhibitor design. (lassak2015argininerhamnosylationasnew pages 10-15, krafczyk2017structuralbasisfor pages 2-3, krafczyk2018exceptionallysweetstudiesonb pages 33-35)
Anti-rhamnosyl-arginine (anti-ArgRha) antibodies were developed that specifically recognize rhamnosylated EF-P and enable sensitive detection of product formation in vitro, enabling kinetic measurements and measurement of intracellular donor pools; these tools were proposed as potentially useful for detecting clinically relevant bacteria carrying this modification system. (krafczyk2018exceptionallysweetstudieson pages 91-94, krafczyk2018exceptionallysweetstudiesonb pages 91-94)
Direct 2023–2024 experimental work specifically on P. putida KT2440 EarP enzymology was not identified in the retrieved corpus. However, two 2024 studies provide important “state of the field” context relevant for annotation and for interpreting EarP presence/absence in genomes:
A 2024 Molecular Biology and Evolution study surveyed >3,000 bacterial genomes, classifying EF-P modification types (including the arginine-EarP type) and analyzing evolutionary dynamics including horizontal gene transfer (HGT). Quantitatively, the authors note many EF-Ps remain untyped (reported as 1,606 genomes encoding EF-Ps of unknown type in their dataset), and they report 10 candidate EF-P HGT events, including 4 involving arginine-EarP systems. This supports that the EarP-associated EF-P activation module is evolutionarily mobile and can shape proteome evolution (e.g., polyproline motif usage). (brewer2024horizontalgenetransfer pages 3-5)
A 2024 bioRxiv preprint explored EF-P variants that function without any PTM, emphasizing that EF-P activity and dependency on modifying enzymes cannot always be inferred solely from motifs. For EarP annotation, this provides an expert-level caution: (i) some bacteria may encode EF-P homologs that do not require PTM; (ii) the presence/absence of EarP and rml genes should be interpreted together with EF-P sequence context and, ideally, proteomic confirmation of modification state. (tomasiunaite2024decryptingthefunctional pages 1-4)
Across the primary mechanistic and structural literature, EarP is consistently presented as a rare but mechanistically tractable example of enzymatic arginine N-glycosylation used to regulate the translation machinery. Structural work emphasizes that EarP belongs to a GT-B-type architecture with physically separable donor/acceptor recognition surfaces, providing concrete residue-level hypotheses for catalysis (acidic residues for acceptor activation; aromatic residues for nucleotide stacking; conserved Arg for leaving-group stabilization). The virulence linkage in P. aeruginosa positions EarP as an anti-virulence target, while the 2024 comparative genomics work highlights its evolutionary importance and mobility among bacteria. (krafczyk2017structuralbasisfor pages 2-3, krafczyk2018exceptionallysweetstudieson pages 45-46, brewer2024horizontalgenetransfer pages 3-5)
| Entity | Summary | Evidence / key details | References |
|---|---|---|---|
| Target identity | EarP / PP_1857 / UniProt Q88LS1 from Pseudomonas putida KT2440; EF-P arginine rhamnosyltransferase | Literature consistently matches the UniProt description: EarP modifies EF-P on Arg32 and belongs to the EarP/GT-B-type glycosyltransferase class, distinct from other EF-P modification systems (krafczyk2017structuralbasisfor pages 2-3, krafczyk2017structuralbasisfor pages 1-2, lassak2015argininerhamnosylationasnew pages 1-10) | Lassak et al., 2015, Nat Chem Biol, https://doi.org/10.1038/nchembio.1751; Krafczyk et al., 2017, mBio, https://doi.org/10.1128/mbio.01412-17 |
| Reaction | Protein-arginine rhamnosylation of EF-P | EarP transfers rhamnose to the guanidino group of EF-P Arg32; reaction is described as inverting, likely SN2-like, producing α-rhamnosyl-arginine on EF-P (krafczyk2018exceptionallysweetstudieson pages 45-46, krafczyk2017structuralbasisfor pages 11-12, krafczyk2018exceptionallysweetstudieson pages 91-94) | Krafczyk et al., 2017, https://doi.org/10.1128/mbio.01412-17; Krafczyk thesis/dissertation evidence, 2018 (krafczyk2018exceptionallysweetstudieson pages 91-94) |
| Donor substrate | dTDP-β-L-rhamnose (TDP-Rha) | In vitro reconstitution required both purified EarP and dTDP-L-rhamnose; intracellular TDP-Rha reported at high micromolar concentrations in E. coli, P. putida, and P. aeruginosa (lassak2015argininerhamnosylationasnew pages 10-15, krafczyk2018exceptionallysweetstudieson pages 91-94, krafczyk2018exceptionallysweetstudiesonb pages 91-94) | Lassak et al., 2015, https://doi.org/10.1038/nchembio.1751; supporting biochemical evidence (krafczyk2018exceptionallysweetstudieson pages 91-94, krafczyk2018exceptionallysweetstudiesonb pages 91-94) |
| Acceptor substrate / site | Translation elongation factor P (EF-P), Arg32 | MS identified +146.058 Da modification on R32-containing EF-P peptides; R32A/R32K variants lost modification; the KOW-like N-domain of EF-P is sufficient for EarP recognition/modification (lassak2015argininerhamnosylationasnew pages 10-15, lassak2015argininerhamnosylationasnew pages 1-10, krafczyk2018exceptionallysweetstudieson pages 45-46) | Lassak et al., 2015, https://doi.org/10.1038/nchembio.1751; Krafczyk et al., 2017, https://doi.org/10.1128/mbio.01412-17 |
| Enzyme family / structure | GT-B-type glycosyltransferase with two opposing Rossmann-like domains | Crystal structure of P. putida EarP bound to TDP-Rha solved at 2.3 Å; donor binds in a conserved C-domain pocket, while EF-P is recognized mainly via the N-domain (krafczyk2017structuralbasisfor pages 2-3, krafczyk2017structuralbasisfor pages 1-2) | Krafczyk et al., 2017, mBio, https://doi.org/10.1128/mbio.01412-17 |
| Key catalytic / binding residues | Likely catalytic residues: D13, D17, E273; donor/leaving-group residues: F252, F258, R271 | D13/D17/E273 proposed to activate the arginine acceptor; D17 + E273 proposed as catalytic dyad; F252/F258 stack with donor thymine/ribose; R271A strongly impairs function, consistent with leaving-group stabilization (krafczyk2018exceptionallysweetstudieson pages 45-46, krafczyk2017structuralbasisfor pages 11-12, krafczyk2018exceptionallysweetstudiesonb pages 45-46) | Krafczyk et al., 2017, https://doi.org/10.1128/mbio.01412-17; supporting mechanistic analyses (krafczyk2018exceptionallysweetstudieson pages 45-46, krafczyk2018exceptionallysweetstudiesonb pages 45-46) |
| Cellular localization | Function is inferred to be cytosolic, acting on the soluble translation factor EF-P in the translation apparatus | EarP modifies EF-P, a bacterial translation elongation factor that acts on ribosomes stalled at polyproline motifs; no evidence in the cited sources supports secretion or membrane localization for EarP itself (krafczyk2017structuralbasisfor pages 2-3, krafczyk2017structuralbasisfor pages 1-2) | Krafczyk et al., 2017, https://doi.org/10.1128/mbio.01412-17; Lassak et al., 2015, https://doi.org/10.1038/nchembio.1751 |
| Biological role | Activates EF-P to alleviate polyproline-induced ribosome stalling | Rhamnosylated EF-P is recruited to stalled ribosomes and promotes peptide-bond formation, especially at problematic polyproline motifs; the modified R32/rhamnose is proposed to stabilize the P-site prolyl-tRNA region (krafczyk2017structuralbasisfor pages 2-3) | Krafczyk et al., 2017, https://doi.org/10.1128/mbio.01412-17 |
| Pathway context | Part of the EF-P post-translational activation pathway coupled to dTDP-L-rhamnose biosynthesis (RmlA-D) | In P. putida KT2440, PP_1782 (RmlC1) and PP_0265 (RmlC2) catalyze the epimerization step, and PP_1784 (RmlD) catalyzes the final reduction to TDP-Rha; this donor is required for EarP-mediated EF-P activation (koller2021twormlchomologs pages 2-4, koller2021functionanddistribution pages 35-38, koller2021twormlchomologs pages 1-2) | Koller & Lassak, 2021, Sci Rep, https://doi.org/10.1038/s41598-021-91421-x |
| Phenotypes / quantitative data | Loss of donor synthesis or modification reduces EF-P-dependent fitness; heterologous rescue depends on TDP-Rha pathway | In an E. coli reporter carrying P. putida efp/earP, loss of rmlC caused roughly 2-fold slower growth versus the intact TDP-Rha pathway background; a genomic screen recovered 12 PP_1782 and 4 PP_0265 complementing clones from ~430,000 clones (~350-fold genome coverage) (koller2021twormlchomologs pages 2-4, koller2021functionanddistribution pages 31-35) | Koller & Lassak, 2021, https://doi.org/10.1038/s41598-021-91421-x |
| Applications / translational relevance | Potential antimicrobial target and pathway marker; relevant to virulence in pathogenic pseudomonads | earP loss abolishes pathogenicity in P. aeruginosa, motivating inhibitor design; anti-ArgRha antibodies enable detection of rhamnosylated EF-P and could support diagnostic or biochemical studies (krafczyk2017structuralbasisfor pages 2-3, krafczyk2018exceptionallysweetstudiesonb pages 33-35, krafczyk2018exceptionallysweetstudieson pages 91-94) | Lassak et al., 2015, https://doi.org/10.1038/nchembio.1751; Krafczyk et al., 2017, https://doi.org/10.1128/mbio.01412-17 |
| Recent developments (2024) | Broader evolutionary and functional context of EarP-type EF-P systems | A 2024 survey across >3,000 bacterial genomes classified EF-P systems and noted arginine-EarP type likely originated in Betaproteobacteria; EarP-type systems were involved in 4 candidate horizontal-transfer events. A 2024 preprint also emphasized that not all EF-P homologs require PTM, sharpening annotation of modification-dependent vs unmodified EF-P systems (brewer2024horizontalgenetransfer pages 3-5, tomasiunaite2024decryptingthefunctional pages 1-4) | Brewer & Wagner, 2024, Mol Biol Evol, https://doi.org/10.1093/molbev/msae180; Tomasiunaite et al., 2024, bioRxiv, https://doi.org/10.1101/2023.09.18.558224 |
Table: This table summarizes the experimentally supported functional annotation of EarP (Q88LS1/PP_1857) in Pseudomonas putida KT2440, including its reaction, substrates, structural class, pathway context, and relevance to physiology and applications. It is useful as a compact evidence map linking UniProt annotation to primary literature and recent evolutionary context.
References
(krafczyk2017structuralbasisfor pages 2-3): Ralph Krafczyk, Jakub Macošek, Pravin Kumar Ankush Jagtap, Daniel Gast, Swetlana Wunder, Prithiba Mitra, Amit Kumar Jha, Jürgen Rohr, Anja Hoffmann-Röder, Kirsten Jung, Janosch Hennig, and Jürgen Lassak. Structural basis for earp-mediated arginine glycosylation of translation elongation factor ef-p. mBio, Nov 2017. URL: https://doi.org/10.1128/mbio.01412-17, doi:10.1128/mbio.01412-17. This article has 36 citations and is from a domain leading peer-reviewed journal.
(krafczyk2017structuralbasisfor pages 1-2): Ralph Krafczyk, Jakub Macošek, Pravin Kumar Ankush Jagtap, Daniel Gast, Swetlana Wunder, Prithiba Mitra, Amit Kumar Jha, Jürgen Rohr, Anja Hoffmann-Röder, Kirsten Jung, Janosch Hennig, and Jürgen Lassak. Structural basis for earp-mediated arginine glycosylation of translation elongation factor ef-p. mBio, Nov 2017. URL: https://doi.org/10.1128/mbio.01412-17, doi:10.1128/mbio.01412-17. This article has 36 citations and is from a domain leading peer-reviewed journal.
(lassak2015argininerhamnosylationasnew pages 10-15): Jürgen Lassak, Eva C Keilhauer, Maximilian Fürst, Kristin Wuichet, Julia Gödeke, Agata L Starosta, Jhong-Min Chen, Lotte Søgaard-Andersen, Jürgen Rohr, Daniel N Wilson, Susanne Häussler, Matthias Mann, and Kirsten Jung. Arginine-rhamnosylation as new strategy to activate translation elongation factor p. Nature chemical biology, 11 4:266-70, Feb 2015. URL: https://doi.org/10.1038/nchembio.1751, doi:10.1038/nchembio.1751. This article has 171 citations and is from a highest quality peer-reviewed journal.
(lassak2015argininerhamnosylationasnew pages 1-10): Jürgen Lassak, Eva C Keilhauer, Maximilian Fürst, Kristin Wuichet, Julia Gödeke, Agata L Starosta, Jhong-Min Chen, Lotte Søgaard-Andersen, Jürgen Rohr, Daniel N Wilson, Susanne Häussler, Matthias Mann, and Kirsten Jung. Arginine-rhamnosylation as new strategy to activate translation elongation factor p. Nature chemical biology, 11 4:266-70, Feb 2015. URL: https://doi.org/10.1038/nchembio.1751, doi:10.1038/nchembio.1751. This article has 171 citations and is from a highest quality peer-reviewed journal.
(krafczyk2018exceptionallysweetstudieson pages 91-94): R Krafczyk. Exceptionally sweet-studies on the bacterial arginine rhamnosyltransferase earp. Unknown journal, 2018.
(krafczyk2018exceptionallysweetstudiesonb pages 91-94): R Krafczyk. Exceptionally sweet-studies on the bacterial arginine rhamnosyltransferase earp. Unknown journal, 2018.
(krafczyk2017structuralbasisfor pages 11-12): Ralph Krafczyk, Jakub Macošek, Pravin Kumar Ankush Jagtap, Daniel Gast, Swetlana Wunder, Prithiba Mitra, Amit Kumar Jha, Jürgen Rohr, Anja Hoffmann-Röder, Kirsten Jung, Janosch Hennig, and Jürgen Lassak. Structural basis for earp-mediated arginine glycosylation of translation elongation factor ef-p. mBio, Nov 2017. URL: https://doi.org/10.1128/mbio.01412-17, doi:10.1128/mbio.01412-17. This article has 36 citations and is from a domain leading peer-reviewed journal.
(krafczyk2018exceptionallysweetstudieson pages 45-46): R Krafczyk. Exceptionally sweet-studies on the bacterial arginine rhamnosyltransferase earp. Unknown journal, 2018.
(koller2021functionanddistribution pages 77-80): Function and distribution of protein mono-glycosylations in bacteria This article has 0 citations.
(koller2021twormlchomologs pages 2-4): Franziska Koller and Jürgen Lassak. Two rmlc homologs catalyze dtdp-4-keto-6-deoxy-d-glucose epimerization in pseudomonas putida kt2440. Scientific Reports, Jun 2021. URL: https://doi.org/10.1038/s41598-021-91421-x, doi:10.1038/s41598-021-91421-x. This article has 9 citations and is from a peer-reviewed journal.
(koller2021functionanddistribution pages 35-38): Function and distribution of protein mono-glycosylations in bacteria This article has 0 citations.
(koller2021twormlchomologs pages 1-2): Franziska Koller and Jürgen Lassak. Two rmlc homologs catalyze dtdp-4-keto-6-deoxy-d-glucose epimerization in pseudomonas putida kt2440. Scientific Reports, Jun 2021. URL: https://doi.org/10.1038/s41598-021-91421-x, doi:10.1038/s41598-021-91421-x. This article has 9 citations and is from a peer-reviewed journal.
(krafczyk2018exceptionallysweetstudiesonb pages 33-35): R Krafczyk. Exceptionally sweet-studies on the bacterial arginine rhamnosyltransferase earp. Unknown journal, 2018.
(brewer2024horizontalgenetransfer pages 3-5): Tess E Brewer and Andreas Wagner. Horizontal gene transfer of a key translation factor and its role in polyproline proteome evolution. Molecular Biology and Evolution, Aug 2024. URL: https://doi.org/10.1093/molbev/msae180, doi:10.1093/molbev/msae180. This article has 8 citations and is from a highest quality peer-reviewed journal.
(tomasiunaite2024decryptingthefunctional pages 1-4): Urte Tomasiunaite, Pavel Kielkowski, Ralph Krafczyk, Ignasi Forné, Axel Imhof, and Kirsten Jung. Decrypting the functional design of unmodified translation elongation factor p. bioRxiv, Sep 2024. URL: https://doi.org/10.1101/2023.09.18.558224, doi:10.1101/2023.09.18.558224. This article has 8 citations.
(krafczyk2018exceptionallysweetstudiesonb pages 45-46): R Krafczyk. Exceptionally sweet-studies on the bacterial arginine rhamnosyltransferase earp. Unknown journal, 2018.
(koller2021functionanddistribution pages 31-35): Function and distribution of protein mono-glycosylations in bacteria This article has 0 citations.