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this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.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 protein A0A2U1PS28 from Artemisia annua (Sweet wormwood) is annotated as a Translation factor GUF1 homolog, mitochondrial (also known as Elongation factor 4, EF-4, or ribosomal back-translocase). While no specific research literature exists for this particular Artemisia annua protein, the GUF1/EF4 family is highly conserved across bacteria, mitochondria, and chloroplasts, allowing functional inference from extensive studies in other organisms (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 7-10, ero2016similarityanddiversity pages 4-7). The protein belongs to the TRAFAC class translation factor GTPase superfamily, with orthologues including bacterial LepA/EF4, yeast mitochondrial Guf1, and mammalian mitochondrial GUF1/mtEF4 (das2023interplaybetweenintersubunit pages 1-2, antolinezfernandez2024molecularpathwaysin pages 5-6).
The Artemisia annua GUF1 homolog functions as a ribosome-dependent GTPase. Unlike metabolic enzymes with small-molecule substrates, GUF1's functional substrate is the ribosome itself, specifically ribosomal complexes in pre-translocational (PRE) or post-translocational (POST) states carrying tRNAs (ero2016similarityanddiversity pages 4-7, antolinezfernandez2024molecularpathwaysin pages 5-6). The enzyme catalyzes GTP hydrolysis in a ribosome-dependent manner, with GTPase activity triggered by interaction with the ribosomal sarcin-ricin loop (SRL) (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 4-7).
The catalytic mechanism of GUF1 involves several conserved structural elements. The G-domain (Domain I) contains the GTP/GDP binding site with characteristic mobile elements including the P-loop, switch I, and switch II regions (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 7-10). The conserved G1 box with the consensus sequence GX₂NXGK(S/T) is critical for nucleotide binding, where the GKS motif specifically contacts the α- and β-phosphates of GTP or GDP (verma2021mrx8theconserved pages 5-6). Studies on related mitochondrial translation GTPases demonstrate that mutation of this GKS motif to AAA completely abolishes in vivo function, confirming the essential requirement for nucleotide binding and hydrolysis (verma2021mrx8theconserved pages 5-6).
The enzyme operates through a GTP-dependent ribosome binding cycle: GUF1 binds to ribosomes with tRNAs in the P and A sites in a GTP-dependent manner, hydrolyzes GTP upon interaction with the ribosome, and undergoes conformational changes that affect ribosome and tRNA positioning (das2023interplaybetweenintersubunit pages 1-2, ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 4-7).
Initial characterization of bacterial LepA/EF4 identified it as a "back-translocase" capable of catalyzing reverse translocation, moving tRNAs from E and P sites back to P and A sites, respectively (ero2016similarityanddiversity pages 4-7). Cryo-electron microscopy studies revealed that EF4 binding to ribosomes results in deacylated tRNA in the P site and peptidyl-tRNA in a distinct A/L site (named for "LepA-induced"), with the acceptor arm shifted away from the peptidyl transferase center (ero2016similarityanddiversity pages 4-7). The unique C-terminal domain of EF4 makes extensive contacts with the acceptor stems of both A-site and P-site tRNAs, contributing to this specialized ribosome interaction mode (das2023interplaybetweenintersubunit pages 1-2, ero2016similarityanddiversity pages 7-10, ero2016similarityanddiversity pages 4-7).
However, recent research indicates that the primary function may not be classical back-translocation but rather translation quality control and fidelity enhancement. Single-molecule FRET measurements demonstrate that LepA preferentially binds PRE-state ribosomes and stabilizes the non-rotated ribosome conformation, contrasting with elongation factor G (EF-G) which favors the rotated conformation (das2023interplaybetweenintersubunit pages 1-2). Studies show that EF4 increases the fraction of active protein synthesized in vitro, suggesting a role in improving translation accuracy rather than simply reversing translocation (xu2022functionsandregulation pages 10-11).
The Artemisia annua GUF1 homolog is predicted to localize to mitochondria based on its N-terminal targeting sequence and sequence homology to characterized mitochondrial GUF1 proteins. Studies of the yeast mitochondrial GTPase Mrx8 (a related YihA family member) demonstrate that such factors localize to the mitochondrial inner membrane facing the matrix side, where they associate with mitochondrial ribosomes (verma2021mrx8theconserved pages 3-5, verma2021mrx8theconserved pages 5-6).
Biochemical fractionation experiments in yeast show that mitochondrial translation GTPases cofractionate with both the small (37S) and large (54S) mitochondrial ribosomal subunits in the presence of magnesium ions and low salt concentrations (verma2021mrx8theconserved pages 5-6, verma2021mrx8theconserved pages 6-7). Treatment with RNase A disrupts this association, demonstrating that the protein requires intact RNA-protein complexes (i.e., assembled ribosomes) for its mitochondrial localization pattern (verma2021mrx8theconserved pages 6-7). This is consistent with the functional requirement for GUF1 to interact directly with translating mitoribosomes.
The mitochondrial localization is critical for GUF1's role in organellar gene expression. Mitochondria maintain their own translation system, producing 13 core subunits of the oxidative phosphorylation (OXPHOS) complexes (wang2021mitochondrialproteintranslation pages 7-8, antolinezfernandez2024molecularpathwaysin pages 5-6). These highly hydrophobic membrane proteins are synthesized by mitochondrial ribosomes (mitoribosomes) using mitochondrially-encoded mRNAs. GUF1 functions as part of the mitochondrial translation elongation machinery alongside other factors including mitochondrial elongation factor Tu (mtEF-Tu), mitochondrial elongation factor Ts (mtEF-Ts), and mitochondrial elongation factor G1 (mtEF-G1) (wang2021mitochondrialproteintranslation pages 7-8, antolinezfernandez2024molecularpathwaysin pages 5-6).
GUF1/mtEF4 is described as a fourth elongation factor in mitochondrial translation, functioning to promote protein synthesis under stress conditions and improve the fidelity of the translation process (antolinezfernandez2024molecularpathwaysin pages 5-6). During mitochondrial translation elongation, mtEF-Tu delivers aminoacyl-tRNA to the A-site of the mitoribosome, peptide bonds are formed at the peptidyl transferase center, and mtEF-G1 catalyzes translocation of the peptidyl-tRNA and mRNA through the ribosome (wang2021mitochondrialproteintranslation pages 7-8, antolinezfernandez2024molecularpathwaysin pages 5-6). GUF1 operates within this cycle, particularly when translation encounters challenging conditions (antolinezfernandez2024molecularpathwaysin pages 5-6).
Studies in Saccharomyces cerevisiae demonstrate that the related mitochondrial GTPase Mrx8 (another YihA family member) is specifically required for optimal synthesis of Cox1 (cytochrome c oxidase subunit 1) at suboptimal temperatures (verma2021mrx8theconserved pages 3-5, verma2021mrx8theconserved pages 5-6). Deletion of MRX8 results in defective de novo Cox1 synthesis at 16°C but not at 30°C, indicating a temperature-dependent function (verma2021mrx8theconserved pages 3-5, verma2021mrx8theconserved pages 5-6). The protein is required for both translation initiation and elongation of Cox1 under cold stress conditions (verma2021mrx8theconserved pages 5-6).
Engineered yeast strains carrying modified mitochondrial DNA demonstrate that Mrx8 preferentially promotes Cox1 synthesis over other mitochondrially-encoded proteins (verma2021mrx8theconserved pages 5-6). Loss of Mrx8 function leads to reduced steady-state levels of Cox1, Cox2, and Cox3, impaired Complex IV assembly and activity, and compromised cellular respiration on non-fermentable carbon sources like glycerol (verma2021mrx8theconserved pages 3-5, verma2021mrx8theconserved pages 5-6). These findings suggest that GUF1 homologs play critical roles in maintaining OXPHOS capacity under physiological or environmental stress.
A consistent feature across GUF1/EF4 family members is their conditional importance under stress conditions. In bacteria, EF4 is non-essential under optimal growth conditions but becomes important under low pH, high magnesium concentrations, low temperature, or antibiotic stress (ero2016similarityanddiversity pages 7-10, ero2016similarityanddiversity pages 4-7). Bacterial cells lacking LepA show growth defects at pH 4 and hypersensitivity to certain antibiotics (ero2016similarityanddiversity pages 4-7).
In bacteria, deletion of lepA reduces the formation of reactive oxygen species (ROS) and increases persister cell survival after treatment with the fluoroquinolone antibiotic ciprofloxacin (braetz2026reducedrosassociatedprophage pages 2-3). This suggests that LepA/EF4 affects translation in ways that influence cellular stress responses, including metabolic pathways that generate ROS (braetz2026reducedrosassociatedprophage pages 2-3). The protein may help translation resume under moderate stress but could contribute to cell death pathways under severe stress (ero2016similarityanddiversity pages 4-7).
Recent evidence suggests that GUF1/EF4 functions in translation quality control rather than simply reversing translation steps. The protein can increase the fraction of correctly folded, active protein synthesized in vitro, indicating a role in translation accuracy (xu2022functionsandregulation pages 10-11). By stabilizing specific ribosome conformations (particularly the non-rotated state), GUF1 may provide additional proofreading time during amino acid incorporation, enhancing translation fidelity (das2023interplaybetweenintersubunit pages 1-2, antolinezfernandez2024molecularpathwaysin pages 5-6).
Competition between EF4 and EF-G for binding to PRE-state ribosomes has been proposed to transiently slow polypeptide elongation, potentially facilitating co-translational protein folding (ero2016similarityanddiversity pages 4-7). Under normal growth conditions, EF-G is approximately 50-fold more abundant than EF4 in bacterial cells, suggesting EF4 plays a specialized rather than routine role in elongation (ero2016similarityanddiversity pages 4-7). However, under stress conditions where EF4 abundance increases, its influence on translation dynamics becomes more significant (ero2016similarityanddiversity pages 4-7).
GUF1/EF4 proteins share a conserved five-domain architecture. Four domains (I, II, III, and V) are topologically equivalent to corresponding domains in elongation factor G (EF-G), while the C-terminal domain (CTD) is unique to the EF4 family (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 7-10).
Domain I (G-domain): The N-terminal GTPase domain consists of a central 6-stranded β-sheet surrounded by 5 α-helices and contains the universally conserved GTP/GDP binding site found in translational GTPases and Ras superfamily GTPases (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 7-10). The domain includes mobile elements (P-loop, switch I, switch II) essential for GTPase activation and conformational changes during the catalytic cycle (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 7-10).
Domain II: Contains a signature twisted β-barrel motif shared among translational GTPases, contributing to the conserved ribosome-binding architecture (ero2016similarityanddiversity pages 7-10).
Domains III and V: Both contain the ribonucleoprotein (RNP) or RNA recognition motif (RRM), consisting of a 4-stranded β-sheet flanked by 2 α-helices (ero2016similarityanddiversity pages 7-10). These domains help position the factor on the ribosome and support its interaction with ribosomal RNA.
C-terminal Domain (CTD): The EF4-specific CTD replaces the domain IV found in EF-G and comprises one long α-helix cradled by four short β-strands (ero2016similarityanddiversity pages 7-10). This unique domain occupies a distinct spatial position compared to both EF-G domain IV and the CTD of the related factor BipA (ero2016similarityanddiversity pages 7-10). Structural studies show that the EF4 CTD makes extensive contacts with ribosome-bound tRNAs, particularly the acceptor stems of both A-site and P-site tRNAs, which is critical for its specialized function in back-translocation-like ribosome remodeling (das2023interplaybetweenintersubunit pages 1-2, ero2016similarityanddiversity pages 7-10, ero2016similarityanddiversity pages 4-7).
GUF1/EF4/LepA is highly conserved across the bacterial domain and persists in eukaryotic organelles descended from bacterial endosymbionts, including mitochondria and chloroplasts (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 7-10, ero2016similarityanddiversity pages 4-7). The protein's broad phylogenetic distribution despite its non-essential nature under optimal conditions supports an ancient and specialized role in translation stress response or quality control (das2023interplaybetweenintersubunit pages 1-2, ero2016similarityanddiversity pages 1-4).
Orthologues have been characterized in:
- Bacteria: LepA/EF4 in Escherichia coli, Salmonella Typhimurium, and other species (ero2016similarityanddiversity pages 7-10, ero2016similarityanddiversity pages 4-7, braetz2026reducedrosassociatedprophage pages 2-3)
- Yeast mitochondria: Guf1 in Saccharomyces cerevisiae (das2023interplaybetweenintersubunit pages 1-2)
- Mammalian mitochondria: mtEF4/GUF1 (wang2021mitochondrialproteintranslation pages 7-8, antolinezfernandez2024molecularpathwaysin pages 5-6)
- Plant organelles: Mitochondrial and chloroplast forms in various plant species (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 7-10)
The high degree of conservation, particularly in the G-domain and nucleotide-binding motifs, indicates that the fundamental GTPase mechanism and ribosome-interaction mode are preserved across all lineages (ero2016similarityanddiversity pages 1-4, verma2021mrx8theconserved pages 5-6).
| Functional Aspect | Description | Evidence Source |
|---|---|---|
| Protein classification and nomenclature | GUF1 is the mitochondrial homolog of bacterial LepA/EF4, a ribosome-dependent translational GTPase in the TRAFAC class; the family is also referred to as translation factor GUF1, elongation factor 4 (EF4), or ribosomal back-translocase. | (das2023interplaybetweenintersubunit pages 1-2, ero2016similarityanddiversity pages 1-4, antolinezfernandez2024molecularpathwaysin pages 5-6) |
| Enzymatic activity and substrate | GUF1/EF4 is a ribosome-dependent GTPase. Its functional substrate is the ribosome, particularly PRE/POST translational complexes carrying tRNAs, rather than a small-molecule metabolite substrate. In vitro work on EF4 shows activity on ribosomal complexes involved in reverse translocation/back-translocation. | (ero2016similarityanddiversity pages 4-7, antolinezfernandez2024molecularpathwaysin pages 5-6) |
| GTPase mechanism | The G domain contains the conserved nucleotide-binding elements typical of translational GTPases, including the P-loop and switch regions; guanine nucleotide binding/hydrolysis is required for function. In the related mitochondrial GTPase Mrx8, mutation of the conserved GKS motif abolishes in vivo function, supporting the importance of GTP binding/hydrolysis in this class. | (ero2016similarityanddiversity pages 1-4, verma2021mrx8theconserved pages 5-6) |
| Primary molecular function | Current understanding supports GUF1/EF4 as a translation quality-control factor that can stabilize specific ribosome conformations and promote back-translocation-like remodeling, thereby improving translation fidelity and helping translation recover under challenging conditions. | (das2023interplaybetweenintersubunit pages 1-2, ero2016similarityanddiversity pages 4-7, antolinezfernandez2024molecularpathwaysin pages 5-6) |
| Subcellular localization | Eukaryotic GUF1 homologs function in mitochondria. Yeast mitochondrial translation GTPases localize to the inner mitochondrial membrane on the matrix side and/or associate with mitoribosomes; mammalian mtEF4/GUF1 is described as a mitochondrial elongation factor. | (verma2021mrx8theconserved pages 3-5, antolinezfernandez2024molecularpathwaysin pages 5-6) |
| Ribosome interaction | EF4/GUF1 binds ribosomes in a GTP-dependent manner, and structural studies show extensive interaction of its unique C-terminal domain with A-site and P-site tRNAs. Single-molecule work indicates LepA stabilizes the non-rotated ribosome conformation. | (das2023interplaybetweenintersubunit pages 1-2, ero2016similarityanddiversity pages 4-7) |
| Role in translation | GUF1/mtEF4 functions in mitochondrial translation elongation control. Reviews place mtEF4/GUF1 alongside mtEF-Tu, mtEF-Ts, and mtEF-G1 as part of the elongation machinery, where it promotes protein synthesis and translation fidelity, particularly when elongation is challenged. | (wang2021mitochondrialproteintranslation pages 7-8, antolinezfernandez2024molecularpathwaysin pages 5-6) |
| Stress response function | EF4/GUF1 is generally dispensable under optimal conditions but becomes important under stress. In bacteria, phenotypes emerge under low pH, high Mg2+, or antibiotic stress; in mitochondria, related translation GTPases are required for efficient synthesis of key respiratory proteins under suboptimal temperature, consistent with a conserved stress-adaptive role for organellar translation factors. | (das2023interplaybetweenintersubunit pages 1-2, ero2016similarityanddiversity pages 7-10, verma2021mrx8theconserved pages 5-6) |
| Structural features | EF4/GUF1 shares four topologically equivalent domains with EF-G (I, II, III, V) plus a unique C-terminal domain instead of EF-G domain IV. The G domain carries the GTP/GDP-binding site, while the EF4-specific CTD comprises a long α-helix cradled by short β-strands and contributes to ribosome/tRNA interactions. | (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 7-10) |
| Evolutionary conservation | EF4/GUF1 is highly conserved across bacteria and persists in eukaryotic organelles, including mitochondria and chloroplasts. This broad conservation, despite conditional phenotypes, supports an ancient and specialized role in safeguarding translation under stress or in difficult elongation states. | (das2023interplaybetweenintersubunit pages 1-2, ero2016similarityanddiversity pages 1-4, antolinezfernandez2024molecularpathwaysin pages 5-6) |
Table: This table summarizes the main conserved functional properties of GUF1/EF4 relevant to annotating the Artemisia annua mitochondrial homolog. It highlights what is directly supported by the literature on EF4/GUF1 family members and what can be inferred for organellar translation function.
| Domain/Region | Structure/Composition | Function | Conservation |
|---|---|---|---|
| Domain I (G-domain) | N-terminal GTPase domain with a central 6-stranded β-sheet surrounded by 5 α-helices; contains the GTP/GDP-binding site and the canonical mobile elements of translational GTPases (switch I, switch II, and P-loop) (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 7-10) | Binds and hydrolyzes guanine nucleotides; mediates ribosome-dependent GTPase activity required for EF4/GUF1 action on translating ribosomes and conformational cycling during translation quality control/back-translocation-like remodeling (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 4-7, antolinezfernandez2024molecularpathwaysin pages 5-6) | Highly conserved across EF-G/EF4/BipA-like translational GTPases and across bacteria and organellar homologs, including mitochondrial GUF1 (das2023interplaybetweenintersubunit pages 1-2, ero2016similarityanddiversity pages 1-4, antolinezfernandez2024molecularpathwaysin pages 5-6) |
| Domain II | Signature twisted β-barrel motif shared among translational GTPases (ero2016similarityanddiversity pages 7-10) | Contributes to the conserved ribosome-binding architecture of EF4 and helps position the factor on the ribosome during elongation-state surveillance (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 4-7) | Conserved and topologically equivalent among EF-G, EF4, and BipA family members (ero2016similarityanddiversity pages 7-10) |
| Domain III | α/β domain containing a 4-stranded β-sheet flanked by 2 α-helices; in EF4 its orientation differs from EF-G, contributing to distinct global conformation (ero2016similarityanddiversity pages 7-10) | Helps shape the overall factor conformation and thereby supports EF4-specific engagement with ribosome states linked to reverse translocation and translation control (ero2016similarityanddiversity pages 7-10, ero2016similarityanddiversity pages 4-7) | Conserved fold shared with EF-G and BipA, though relative orientation varies and likely underlies functional divergence (ero2016similarityanddiversity pages 7-10) |
| Domain V | α/β domain with a 4-stranded β-sheet flanked by 2 α-helices; directly contacts the G-domain in EF4, unlike the rotated arrangement seen in BipA (ero2016similarityanddiversity pages 7-10) | Participates in the common translational GTPase scaffold and supports ribosome interaction and factor conformational organization during translation (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 7-10) | Conserved topologically among EF-G/EF4/BipA-like factors (ero2016similarityanddiversity pages 7-10) |
| C-terminal domain (CTD) | EF4-specific domain replacing EF-G domain IV; comprises one long α-helix cradled by four short β-strands and occupies a distinct position from BipA CTD and EF-G domain IV (ero2016similarityanddiversity pages 7-10) | Makes extensive contacts with ribosome-bound tRNAs; structural studies indicate interaction with acceptor stems of A-site and P-site tRNAs and support EF4/GUF1 roles in back-translocation-like remodeling and stabilization of specific ribosome conformations (das2023interplaybetweenintersubunit pages 1-2, ero2016similarityanddiversity pages 7-10, ero2016similarityanddiversity pages 4-7) | Characteristic of EF4/GUF1 family and absent from canonical EF-G, helping define EF4-specific function despite the shared core with other translational GTPases (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 7-10) |
| G1 box / GKS motif | Conserved nucleotide-binding sequence motif within the G-domain; in related mitochondrial translation GTPases, the G1 box follows the GX2NXGK(S/T) consensus, and the GKS residues contact the α- and β-phosphates of GDP/GTP (verma2021mrx8theconserved pages 5-6) | Essential for guanine nucleotide binding and therefore for in vivo function; mutational disruption of the GKS motif abolishes translation-associated activity in mitochondrial ribosome-associated GTPases, supporting the same mechanistic requirement for GUF1/EF4 family members (verma2021mrx8theconserved pages 5-6) | Strongly conserved across TRAFAC-family ribosome-associated GTPases and consistent with UniProt domain assignment for A0A2U1PS28 as a translation-factor GTPase (ero2016similarityanddiversity pages 1-4, verma2021mrx8theconserved pages 5-6) |
| Switch regions | Conserved mobile elements of the G-domain, including switch I and switch II, typical of translational GTPases (ero2016similarityanddiversity pages 7-10) | Transmit nucleotide state to conformational changes that regulate ribosome engagement, GTP hydrolysis, and release; central to coupling guanine nucleotide state with EF4/GUF1 action on the ribosome (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 4-7) | Broadly conserved among translational GTPases, including EF-G, EF4, and organellar GUF1 homologs (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 7-10) |
| P-loop | Conserved phosphate-binding loop within the G-domain nucleotide-binding pocket (ero2016similarityanddiversity pages 7-10) | Coordinates phosphate groups of bound GDP/GTP and is fundamental to ribosome-dependent GTPase activity during translation factor cycling (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 4-7) | Universally conserved hallmark of Ras-like/TRAFAC GTPases and retained in EF4/GUF1 family proteins (ero2016similarityanddiversity pages 1-4, ero2016similarityanddiversity pages 7-10) |
Table: This table summarizes the conserved structural architecture of GUF1/EF4 and links individual domains and motifs to their known or inferred roles in ribosome-dependent GTPase activity and mitochondrial translation. It is useful for functional annotation of the Artemisia annua GUF1 homolog by separating well-supported structural features from mechanistic inference.
Based on the extensive literature on GUF1/EF4 homologs across organisms, the Artemisia annua A0A2U1PS28 protein can be functionally annotated as:
Primary Function: A mitochondrial translation elongation factor functioning as a ribosome-dependent GTPase that promotes translation quality control, particularly under stress conditions.
Enzymatic Activity: GTP hydrolase (EC 3.6.5.n1) with ribosome-dependent GTPase activity. The substrate is the mitochondrial ribosome in complex with tRNAs during translation elongation.
Substrate Specificity: Binds to mitochondrial ribosomes (mitoribosomes) in PRE or POST translational states, with preference for ribosomes carrying tRNAs in P and A sites. Shows specific requirement for mitochondrial rRNA and ribosomal proteins for activation of GTPase activity.
Mechanism of Action: Binds GTP and associates with translating mitoribosomes through interactions with ribosomal RNA (particularly the sarcin-ricin loop) and ribosome-bound tRNAs. Upon ribosome binding, undergoes GTP hydrolysis, leading to conformational changes that can induce back-translocation-like movements of tRNAs or stabilize specific ribosome conformations that enhance translation fidelity.
Subcellular Localization: Mitochondrial matrix and inner mitochondrial membrane, where it associates with the mitochondrial translation machinery.
Biological Role: Functions in the mitochondrial translation pathway to ensure optimal synthesis of OXPHOS complex subunits, particularly under environmental or physiological stress conditions. May be especially important for Cox1 synthesis and Complex IV biogenesis. Contributes to translation accuracy and ribosome rescue mechanisms.
Pathway Context: Operates within the mitochondrial protein synthesis pathway alongside mtEF-Tu, mtEF-Ts, and mtEF-G1 as part of the elongation machinery. Functions in the broader context of mitochondrial OXPHOS biogenesis and cellular energy metabolism.
The functional conservation of GUF1/EF4 across bacteria and eukaryotic organelles, combined with its specialized stress-response role, suggests that the Artemisia annua protein likely serves similar functions in maintaining mitochondrial translation under challenging growth conditions, which may be particularly relevant for plants adapting to environmental stresses.
References
(ero2016similarityanddiversity pages 1-4): Rya Ero, Veerendra Kumar, Yun Chen, and Yong-Gui Gao. Similarity and diversity of translational gtpase factors ef-g, ef4, and bipa: from structure to function. RNA Biology, 13:1258-1273, Nov 2016. URL: https://doi.org/10.1080/15476286.2016.1201627, doi:10.1080/15476286.2016.1201627. This article has 26 citations and is from a peer-reviewed journal.
(ero2016similarityanddiversity pages 7-10): Rya Ero, Veerendra Kumar, Yun Chen, and Yong-Gui Gao. Similarity and diversity of translational gtpase factors ef-g, ef4, and bipa: from structure to function. RNA Biology, 13:1258-1273, Nov 2016. URL: https://doi.org/10.1080/15476286.2016.1201627, doi:10.1080/15476286.2016.1201627. This article has 26 citations and is from a peer-reviewed journal.
(ero2016similarityanddiversity pages 4-7): Rya Ero, Veerendra Kumar, Yun Chen, and Yong-Gui Gao. Similarity and diversity of translational gtpase factors ef-g, ef4, and bipa: from structure to function. RNA Biology, 13:1258-1273, Nov 2016. URL: https://doi.org/10.1080/15476286.2016.1201627, doi:10.1080/15476286.2016.1201627. This article has 26 citations and is from a peer-reviewed journal.
(das2023interplaybetweenintersubunit pages 1-2): Ananya Das, Nichole Adiletta, and Dmitri N. Ermolenko. Interplay between inter-subunit rotation of the ribosome and binding of translational gtpases. International Journal of Molecular Sciences, 24:6878, Apr 2023. URL: https://doi.org/10.3390/ijms24086878, doi:10.3390/ijms24086878. This article has 2 citations.
(antolinezfernandez2024molecularpathwaysin pages 5-6): Álvaro Antolínez-Fernández, Paula Esteban-Ramos, Miguel Ángel Fernández-Moreno, and Paula Clemente. Molecular pathways in mitochondrial disorders due to a defective mitochondrial protein synthesis. Frontiers in Cell and Developmental Biology, May 2024. URL: https://doi.org/10.3389/fcell.2024.1410245, doi:10.3389/fcell.2024.1410245. This article has 16 citations.
(verma2021mrx8theconserved pages 5-6): Yash Verma, Upasana Mehra, Dharmendra Kumar Pandey, Joy Kar, Xochitl Pérez-Martinez, Siddhartha S. Jana, and Kaustuv Datta. mrx8, the conserved mitochondrial yiha gtpase family member, is required for de novo cox1 synthesis at suboptimal temperatures in saccharomyces cerevisiae. Nov 2021. URL: https://doi.org/10.1091/mbc.e20-07-0457, doi:10.1091/mbc.e20-07-0457. This article has 11 citations and is from a domain leading peer-reviewed journal.
(xu2022functionsandregulation pages 10-11): Benjin Xu, Ling Liu, and Guangtao Song. Functions and regulation of translation elongation factors. Frontiers in Molecular Biosciences, Jan 2022. URL: https://doi.org/10.3389/fmolb.2021.816398, doi:10.3389/fmolb.2021.816398. This article has 114 citations.
(verma2021mrx8theconserved pages 3-5): Yash Verma, Upasana Mehra, Dharmendra Kumar Pandey, Joy Kar, Xochitl Pérez-Martinez, Siddhartha S. Jana, and Kaustuv Datta. mrx8, the conserved mitochondrial yiha gtpase family member, is required for de novo cox1 synthesis at suboptimal temperatures in saccharomyces cerevisiae. Nov 2021. URL: https://doi.org/10.1091/mbc.e20-07-0457, doi:10.1091/mbc.e20-07-0457. This article has 11 citations and is from a domain leading peer-reviewed journal.
(verma2021mrx8theconserved pages 6-7): Yash Verma, Upasana Mehra, Dharmendra Kumar Pandey, Joy Kar, Xochitl Pérez-Martinez, Siddhartha S. Jana, and Kaustuv Datta. mrx8, the conserved mitochondrial yiha gtpase family member, is required for de novo cox1 synthesis at suboptimal temperatures in saccharomyces cerevisiae. Nov 2021. URL: https://doi.org/10.1091/mbc.e20-07-0457, doi:10.1091/mbc.e20-07-0457. This article has 11 citations and is from a domain leading peer-reviewed journal.
(wang2021mitochondrialproteintranslation pages 7-8): Fei Wang, Deyu Zhang, Dejiu Zhang, Peifeng Li, and Yanyan Gao. Mitochondrial protein translation: emerging roles and clinical significance in disease. Frontiers in Cell and Developmental Biology, Jul 2021. URL: https://doi.org/10.3389/fcell.2021.675465, doi:10.3389/fcell.2021.675465. This article has 144 citations.
(braetz2026reducedrosassociatedprophage pages 2-3): Sebastian Braetz, Magdalena Karp, Andreas Nerlich, and Marcus Fulde. Reduced ros-associated prophage induction in a lepa mutant contributes to increased fluoroquinolone persistence in salmonella typhimurium. Scientific Reports, Apr 2026. URL: https://doi.org/10.1038/s41598-026-47552-0, doi:10.1038/s41598-026-47552-0. This article has 0 citations and is from a peer-reviewed journal.