Group 3 late-embryogenesis abundant (LEA) protein targeted to the mitochondrial matrix in the anhydrobiotic tardigrade Ramazzottius varieornatus. RvLEAM contains 9 LEA 11-mer repeat motifs that form amphipathic helices under water-deficient conditions, acting as a molecular shield to prevent undesirable protein aggregation and conformational changes of lipid membranes. A predicted 31-residue mitochondrial transit peptide directs the protein to the mitochondrial matrix. Heterologous expression in human cells improves osmotic tolerance, consistent with a protective role during desiccation stress. RvLEAM belongs to the LEA type 4 family, which is broadly conserved across plants, nematodes, and other anhydrobiotic organisms.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0005739
mitochondrion
|
IEA
GO_REF:0000044 |
MODIFY |
Summary: Mitochondrial localization is strongly supported by multiple lines of evidence in PMID:25675104. Immunohistochemistry confirmed mitochondrial localization in tardigrade cells, and RvLEAM-GFP co-localized with MitoTracker Red in human cells. The IEA annotation to the broad term 'mitochondrion' could be refined to 'mitochondrial matrix' (GO:0005759) given that the protein is highly hydrophilic (GRAVY score -0.94, no hydrophobic regions), which strongly suggests matrix rather than membrane localization (PMID:25675104). UniProt annotates a mitochondrial transit peptide at residues 1-31.
Reason: The annotation to GO:0005739 (mitochondrion) is correct but insufficiently specific. RvLEAM has a predicted mitochondrial transit peptide (residues 1-31) and is highly hydrophilic with no hydrophobic regions, strongly suggesting localization in the mitochondrial matrix rather than the membrane. The more specific term GO:0005759 (mitochondrial matrix) is warranted based on both the experimental localization data and biophysical properties of the protein.
Proposed replacements:
mitochondrial matrix
Supporting Evidence:
PMID:25675104
RvLEAM is a group3 LEA protein and immunohistochemistry confirmed its mitochondrial localization in tardigrade cells
PMID:25675104
we identified two novel mitochondrial heat-soluble proteins, RvLEAM and MAHS (Mitochondrial Abundant Heat Soluble), as potent mitochondrial protectants from Ramazzottius varieornatus
|
|
GO:0009269
response to desiccation
|
IDA
PMID:25675104 Novel mitochondria-targeted heat-soluble proteins identified... |
NEW |
Summary: RvLEAM is a group 3 LEA protein identified from the anhydrobiotic tardigrade R. varieornatus (PMID:25675104). LEA proteins are well-established components of the desiccation tolerance response in plants, nematodes, and other anhydrobiotic organisms. The protein is described as having protective roles in water-deficient environments, and its expression improves hyperosmotic tolerance of human cells. UniProt annotates this protein with the keyword "Stress response" and describes it as acting as a molecular shield in water-deficient conditions.
Reason: This is a core biological process annotation that is missing from GOA. RvLEAM is a LEA protein involved in desiccation tolerance, and its expression improves tolerance to water-deficient conditions. The response to desiccation annotation captures the primary biological context of this protein.
Supporting Evidence:
PMID:25675104
Late Embryogenesis Abundant (LEA) proteins are heat-soluble proteins involved in the desiccation tolerance of many anhydrobiotic organisms
PMID:25675104
tardigrade mitochondria contain at least two types of heat-soluble proteins that might have protective roles in water-deficient environments
|
|
GO:0006970
response to osmotic stress
|
IDA
PMID:25675104 Novel mitochondria-targeted heat-soluble proteins identified... |
NEW |
Summary: Tanaka et al. (PMID:25675104) directly demonstrated that expression of RvLEAM improved hyperosmotic tolerance of human HEp-2 cells. This provides direct experimental evidence for a role in response to osmotic stress.
Reason: Direct experimental evidence from PMID:25675104 supports this annotation. RvLEAM expression improved hyperosmotic tolerance in human cells, demonstrating the protein functions in the cellular response to osmotic stress. This is the most directly tested biological process for this protein.
Supporting Evidence:
PMID:25675104
we demonstrated that RvLEAM protein as well as MAHS protein improved the hyperosmotic tolerance of human cells
|
|
GO:0051082
unfolded protein binding
|
IDA
PMID:25675104 Novel mitochondria-targeted heat-soluble proteins identified... |
NEW |
Summary: LEA proteins are known to act as molecular shields that interact with other macromolecules to prevent undesirable aggregation under water stress conditions. While this implies interaction with proteins that may become aggregation-prone, direct binding to unfolded proteins was not experimentally demonstrated for RvLEAM specifically in PMID:25675104. The molecular shield mechanism is inferred from the general LEA protein family literature. This annotation captures the likely molecular function but should be considered provisional.
Reason: The molecular shield function of LEA proteins involves preventing protein aggregation under stress, which is consistent with unfolded protein binding. However, this is inferred from the general LEA protein literature rather than direct experimental demonstration for RvLEAM. This annotation captures the likely molecular function mechanism but should be considered provisional pending direct binding studies.
Supporting Evidence:
PMID:25675104
tardigrade mitochondria contain at least two types of heat-soluble proteins that might have protective roles in water-deficient environments
|
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template_file: templates/gene_research_go_focused.md
template_variables:
organism: RAMVA
gene_id: RvLEAM
gene_symbol: RvLEAM
uniprot_accession: A0A0E4AVP3
protein_description: 'RecName: Full=Group 3 late-embryogenesis abundant protein,
mitochondrial {ECO:0000303|PubMed:25675104}; Short=LEAM {ECO:0000303|PubMed:25675104};
Flags: Precursor;'
gene_info: Name=RvLEAM {ECO:0000303|PubMed:25675104}; ORFNames=RvY_15023;
organism_full: Ramazzottius varieornatus (Water bear) (Tardigrade).
protein_family: Belongs to the LEA type 4 family. .
protein_domains: Not specified in UniProt
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citation_count: 24
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'RvLEAM' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene RvLEAM (gene ID: RvLEAM, UniProt: A0A0E4AVP3) in RAMVA.
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.
Question: You are an expert researcher providing comprehensive, well-cited information.
Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies
Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'RvLEAM' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene RvLEAM (gene ID: RvLEAM, UniProt: A0A0E4AVP3) in RAMVA.
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 target gene/protein in this report is RvLEAM from the tardigrade Ramazzottius varieornatus (water bear), matching the UniProt entry A0A0E4AVP3, described as a mitochondrial Group 3 late-embryogenesis abundant (LEA) protein (often referred to as LEAM) (tanaka2015novelmitochondriatargetedheatsoluble pages 2-4). The defining primary paper (peer-reviewed) explicitly names and characterizes RvLEAM as a mitochondrial LEA protein from R. varieornatus and provides both native-organism and heterologous localization experiments (tanaka2015novelmitochondriatargetedheatsoluble pages 5-7, tanaka2015novelmitochondriatargetedheatsoluble pages 2-4). No evidence in the retrieved corpus suggests an alternative gene with the same symbol in another organism; thus, the symbol is treated as unambiguous in this context (tanaka2015novelmitochondriatargetedheatsoluble pages 2-4).
LEA proteins are classically described as highly hydrophilic, stress-associated proteins that are typically intrinsically disordered in aqueous conditions but can acquire α-helical structure under water deficit. Mechanistic models emphasize protection of other macromolecules through molecular shielding/anti-aggregation, membrane stabilization, and contributions to vitrification/glass-like states in the dry cytoplasm (hand2018challengesduringdiapause pages 8-8, romeroperez2023whenphasedwithout pages 22-23). A recent high-authority synthesis (Chemical Reviews, 2023) also frames LEA/hydrophilin protection in terms of hydration-dependent phase/material properties, including effects on vitrification and protective assemblies (romeroperez2023whenphasedwithout pages 11-12, romeroperez2023whenphasedwithout pages 22-23).
Group 3 LEA proteins are commonly enriched for repeated short motifs and are frequently predicted to form amphipathic α-helices under dehydration-like conditions, consistent with “molecular shield” and membrane-protective models (yoshida2022decipheringthebiological pages 4-6, romeroperez2023whenphasedwithout pages 22-23).
Mitochondria are major sites of stress vulnerability during dehydration/rehydration (bioenergetic collapse, membrane perturbation, ROS). Mitochondria-targeted LEA proteins are therefore hypothesized to provide organelle-localized protection via the same physical-chemical modes (shielding, membrane stabilization, glass modulation) but focused on mitochondrial matrices and membranes (hand2018challengesduringdiapause pages 8-8). In tardigrades, mitochondrial-localized heat-soluble proteins including RvLEAM were described as candidate mitochondrial protectants (schill2019environmentaladaptationsdesiccation pages 10-13).
Tanaka et al. (2015) report that RvLEAM shows sequence similarity to nematode LEA proteins (e-value < 1e−05) and matches a LEA-related motif (PTHR23241), supporting its assignment as a canonical LEA-family protein rather than a tardigrade-unique disordered protein family (tanaka2015novelmitochondriatargetedheatsoluble pages 4-5). They identify nine LEA-like 11-mer motifs, consistent with group 3 LEA architecture and predicted helical repeats (tanaka2015novelmitochondriatargetedheatsoluble pages 4-5).
Physicochemical predictions show RvLEAM is highly hydrophilic (GRAVY −0.94) with no strong hydrophobic segment, consistent with a soluble protein. The absence of a transmembrane region led the authors to infer mitochondrial matrix localization rather than membrane insertion (tanaka2015novelmitochondriatargetedheatsoluble pages 4-5). Secondary-structure prediction suggested long helical regions and putative amphipathic helices (tanaka2015novelmitochondriatargetedheatsoluble pages 4-5), aligning with prevailing LEA models in which amphipathic helices interact with protein or membrane surfaces during dehydration/osmotic stress (yoshida2022decipheringthebiological pages 4-6, romeroperez2023whenphasedwithout pages 22-23).
Multiple predictors (TargetP, WoLF PSORT, MitoProt2) supported mitochondrial targeting; TargetP predicted a 31-aa N-terminal mitochondrial targeting peptide (tanaka2015novelmitochondriatargetedheatsoluble pages 5-7, tanaka2015novelmitochondriatargetedheatsoluble pages 4-5).
In human HEp-2 cells, an RvLEAM–GFP fusion co-localized with mitochondria stained by MitoTracker, while GFP alone was diffuse (tanaka2015novelmitochondriatargetedheatsoluble pages 5-7). A cropped figure region showing this co-localization (Figure 1d in the original paper) was retrieved (tanaka2015novelmitochondriatargetedheatsoluble media 470ae241).
Immunohistochemistry in R. varieornatus embryos detected RvLEAM signal broadly across cells and mostly merged with ATP5A, a mitochondrial marker, providing direct evidence that RvLEAM localizes to mitochondria in the native organism (tanaka2015novelmitochondriatargetedheatsoluble pages 5-7).
A defining biochemical feature reported for RvLEAM is heat solubility. Recombinant RvLEAM expressed in bacteria remained largely in the soluble fraction after high-temperature treatment, and purified RvLEAM alone was also heat-soluble (tanaka2015novelmitochondriatargetedheatsoluble pages 5-7). Heat-solubility is consistent with LEA proteins being enriched in disorder and resistant to aggregation during stress, enabling them to function under extreme physicochemical conditions (romeroperez2023whenphasedwithout pages 22-23).
Tanaka et al. used stable HEp-2 lines expressing RvLEAM and challenged cells with 100–350 mM sucrose for 48 h, using a PrestoBlue reducing-power assay to quantify relative metabolic activity (normalized to 0 mM sucrose; n=3, SEM; Dunnett’s test) (tanaka2015novelmitochondriatargetedheatsoluble pages 10-11, tanaka2015novelmitochondriatargetedheatsoluble pages 4-5). RvLEAM-expressing cells exhibited significantly improved tolerance across conditions, including an approximately two-fold increase in metabolic activity at 300 mM sucrose and at least ~10% improvement across tested concentrations (tanaka2015novelmitochondriatargetedheatsoluble pages 10-11). A cropped region containing the hyperosmotic tolerance plot (Figure 5) was retrieved (tanaka2015novelmitochondriatargetedheatsoluble media 129a06d0).
Interpretation: This experiment provides direct functional evidence that RvLEAM can enhance cellular performance under osmotic/water stress when targeted to mitochondria, consistent with mitochondrial protection being a key bottleneck in anhydrobiotic/cryptobiotic survival (tanaka2015novelmitochondriatargetedheatsoluble pages 10-11, hand2018challengesduringdiapause pages 8-8).
No enzymatic catalytic activity is reported for RvLEAM; instead, evidence supports RvLEAM as a non-enzymatic, stress-protective, organelle-localized protein. The best-supported functional model is that RvLEAM contributes to tolerance of water/osmotic stress by protecting mitochondrial components (proteins and/or membranes) via LEA-like physical mechanisms (molecular shielding, stabilization of macromolecular assemblies, modulation of dry-state material properties) (hand2018challengesduringdiapause pages 8-8, yoshida2022decipheringthebiological pages 4-6, romeroperez2023whenphasedwithout pages 22-23).
While RvLEAM itself was not demonstrated to induce gels/condensates (those observations are stronger for tardigrade CAHS-family proteins), broader desiccation biology emphasizes that protective IDPs/LEA proteins can influence vitrification/glass transition behavior and hydration-dependent phase/material transitions, which may be central to survival in dry states (romeroperez2023whenphasedwithout pages 11-12, romeroperez2023whenphasedwithout pages 22-23). Thus, RvLEAM’s predicted amphipathic helical segments and heat-solubility are consistent with canonical LEA modes of action (tanaka2015novelmitochondriatargetedheatsoluble pages 4-5, romeroperez2023whenphasedwithout pages 22-23).
A 2023 Chemical Reviews article synthesized modern understanding of desiccation tolerance across biomolecules and condensate/material-state changes, discussing how IDPs (including LEA/hydrophilins and tardigrade disordered proteins) can protect through molecular shielding, gelation/solidification, and effects on vitrification and diffusion in drying cells (romeroperez2023whenphasedwithout pages 11-12, romeroperez2023whenphasedwithout pages 22-23). This provides up-to-date conceptual scaffolding for interpreting RvLEAM as a mitochondrial-localized component of a broader stress-protective material strategy.
A major 2024 development is the repurposing of RvLEAM as a practical additive for cryo-electron microscopy sample preparation. Abe et al. (Nature Communications, 2024-09-xx) used a truncated construct RvLEAMshort (~15 kDa) derived from R. varieornatus RvLEAM to mitigate air–water interface (AWI) damage during plunge freezing (abe2024smallleaproteinsa pages 2-3). In reported datasets, adding RvLEAMshort at 1:6 sample:RvLEAMshort enabled reconstructions at 4.5 Å (polymerase α-primase) and 3.7 Å (PRC2) (abe2024smallleaproteinsa pages 2-3, abe2024smallleaproteinsa pages 4-5).
Quantitatively, in a crosslinked PRC2 control without RvLEAMshort only ~3% of ~1.7 million picked particles contributed to the final map, whereas with RvLEAMshort ~14% of ~2.5 million picked particles contributed, indicating higher particle usability/retention (abe2024smallleaproteinsa pages 4-5). Orientation isotropy improved substantially (sphericity up to 0.97 with crosslinking + RvLEAMshort) and a 3.1 Å map was obtained under a 10-min crosslink condition (abe2024smallleaproteinsa pages 5-6, abe2024smallleaproteinsa pages 3-4).
Relevance to functional annotation: Although this is an ex vivo application, it strongly supports the concept that LEA proteins (including a tardigrade mitochondrial LEA) can act as surface-active protective agents under extreme interfacial stress—consistent with “molecular shielding” and stress stabilization frameworks (abe2024smallleaproteinsa pages 2-3, romeroperez2023whenphasedwithout pages 22-23).
1) Cell stress-engineering concept: RvLEAM expression in human cells improves survival/metabolic activity under hyperosmotic stress (tanaka2015novelmitochondriatargetedheatsoluble pages 10-11). While not yet a deployed clinical/industrial product in the retrieved sources, this is a concrete demonstration of translational potential (engineering mitochondrial protectants for cell preservation or stress resilience).
2) Structural biology workflow additive (implemented in practice): RvLEAMshort is used as an AWI protectant in cryo-EM grid preparation to enable/accelerate high-resolution structure determination for fragile complexes, with explicit workflow parameters and quantitative improvements in particle retention and orientation distribution (abe2024smallleaproteinsa pages 2-3, abe2024smallleaproteinsa pages 4-5).
A tardigrade-focused review of anhydrobiosis genomics emphasizes that LEA proteins are typically hydrophilic and unstructured, can form amphipathic helices under water deficit, and that mitochondrial-localized examples (including RvLEAM) can improve hyperosmotic tolerance in human cells—supporting the view of RvLEAM as a mitochondria-targeted protectant (yoshida2022decipheringthebiological pages 4-6). More broadly, the Chemical Reviews synthesis highlights that while multiple protective IDP families exist, the molecular rules remain incompletely resolved, and dry-state biology likely involves coupled effects on diffusion, glass transitions, and biomolecular phase behavior (romeroperez2023whenphasedwithout pages 11-12).
The following table consolidates major claims, evidence types, quantitative outcomes, and metadata.
| Claim/Aspect | Key findings | Evidence type | Source (paper, year, journal) | URL | Pub date | Citation ID |
|---|---|---|---|---|---|---|
| Identity | RvLEAM is the group 3 late-embryogenesis abundant mitochondrial protein from Ramazzottius varieornatus; literature description matches UniProt A0A0E4AVP3 and identifies it as a mitochondrial LEA-family protein from a tardigrade. | Primary literature synthesis | Tanaka et al., 2015, PLoS ONE; Yoshida & Tanaka, 2022, Insects | https://doi.org/10.1371/journal.pone.0118272 ; https://doi.org/10.3390/insects13060557 | 2015-02 ; 2022-06 | (tanaka2015novelmitochondriatargetedheatsoluble pages 2-4, yoshida2022decipheringthebiological pages 4-6) |
| Localization | Multiple targeting predictors (TargetP, WoLF PSORT, MitoProt2) supported mitochondrial targeting; TargetP predicted a 31-aa N-terminal mitochondrial targeting peptide. | Computational | Tanaka et al., 2015, PLoS ONE | https://doi.org/10.1371/journal.pone.0118272 | 2015-02 | (tanaka2015novelmitochondriatargetedheatsoluble pages 5-7, tanaka2015novelmitochondriatargetedheatsoluble pages 4-5) |
| Localization | RvLEAM-GFP co-localized with MitoTracker in human HEp-2 cells, while GFP alone was diffuse, demonstrating mitochondrial targeting in a heterologous system. Figure support available for mitochondrial localization. | Heterologous cells | Tanaka et al., 2015, PLoS ONE | https://doi.org/10.1371/journal.pone.0118272 | 2015-02 | (tanaka2015novelmitochondriatargetedheatsoluble pages 5-7, tanaka2015novelmitochondriatargetedheatsoluble media 470ae241) |
| Localization | Immunohistochemistry in tardigrade embryos showed RvLEAM signal in almost all cells and mostly merged with ATP5A, a mitochondrial marker, supporting in vivo mitochondrial localization in the native organism. | In vivo tardigrade | Tanaka et al., 2015, PLoS ONE | https://doi.org/10.1371/journal.pone.0118272 | 2015-02 | (tanaka2015novelmitochondriatargetedheatsoluble pages 5-7) |
| Structure/biophysics | RvLEAM showed similarity to nematode LEA proteins (e-value < 1e-05), matched the LEA-RELATED motif (PTHR23241), and contained 9 LEA-like 11-mer motifs, consistent with a canonical group 3 LEA architecture. | Computational / sequence analysis | Tanaka et al., 2015, PLoS ONE | https://doi.org/10.1371/journal.pone.0118272 | 2015-02 | (tanaka2015novelmitochondriatargetedheatsoluble pages 4-5) |
| Structure/biophysics | Predicted to be highly hydrophilic (GRAVY = -0.94), lacking a clear hydrophobic transmembrane segment, suggesting matrix localization rather than membrane integration. Secondary-structure prediction indicated long helical regions and putative amphipathic helices. | Computational | Tanaka et al., 2015, PLoS ONE | https://doi.org/10.1371/journal.pone.0118272 | 2015-02 | (tanaka2015novelmitochondriatargetedheatsoluble pages 4-5) |
| Biochemical properties | Recombinant RvLEAM remained largely in the supernatant after heat treatment, and purified protein alone was heat-soluble, matching the characteristic heat-solubility of LEA proteins. | In vitro | Tanaka et al., 2015, PLoS ONE | https://doi.org/10.1371/journal.pone.0118272 | 2015-02 | (tanaka2015novelmitochondriatargetedheatsoluble pages 5-7) |
| Functional assays | In stable human HEp-2 cells, RvLEAM expression increased tolerance to hyperosmotic sucrose challenge (100-350 mM added sucrose for 48 h). Reported effects included a ~2-fold increase in metabolic activity at 300 mM sucrose and ≥10% improvement across all tested osmotic conditions. | Heterologous cells | Tanaka et al., 2015, PLoS ONE | https://doi.org/10.1371/journal.pone.0118272 | 2015-02 | (tanaka2015novelmitochondriatargetedheatsoluble pages 10-11, tanaka2015novelmitochondriatargetedheatsoluble media 129a06d0) |
| Functional interpretation | Reviews summarize RvLEAM as a mitochondrial LEA that, like other LEA proteins, is hydrophilic, largely unstructured in water, can adopt amphipathic helices during dehydration, and likely acts as a molecular shield protecting proteins/lipids under water stress. | Expert review / mechanistic inference | Yoshida & Tanaka, 2022, Insects | https://doi.org/10.3390/insects13060557 | 2022-06 | (yoshida2022decipheringthebiological pages 4-6) |
| Applications | A truncated construct, RvLEAMshort (~15 kDa), derived from the tardigrade RvLEAM, was used as an additive to protect fragile cryo-EM samples from air-water interface damage during plunge freezing. | Real-world implementation / biotechnology | Abe et al., 2024, Nature Communications | https://doi.org/10.1038/s41467-024-52091-1 | 2024-09 | (abe2024smallleaproteinsa pages 2-3) |
| Applications | In cryo-EM, sample:RvLEAMshort = 1:6 improved particle recovery and enabled reconstructions of 4.5 Å for polymerase α-primase (PP) and 3.7 Å for PRC2 from single-night data collections. | Real-world implementation / structural biology | Abe et al., 2024, Nature Communications | https://doi.org/10.1038/s41467-024-52091-1 | 2024-09 | (abe2024smallleaproteinsa pages 2-3, abe2024smallleaproteinsa pages 4-5) |
| Applications | For PRC2, adding RvLEAMshort plus crosslinking improved orientation isotropy and resolution: sphericity increased from 0.79 (no crosslink) to 0.83 (2 min crosslink) and 0.97 (10 min crosslink), with a 3.1 Å map after 10 min crosslinking. | Real-world implementation / structural biology | Abe et al., 2024, Nature Communications; Abe & Lim, 2024, bioRxiv | https://doi.org/10.1038/s41467-024-52091-1 ; https://doi.org/10.1101/2024.02.06.579238 | 2024-09 ; 2024-02 | (abe2024smallleaproteinsa pages 5-6, abe2024smallleaproteinsa pages 3-4) |
| Applications | In a crosslinked PRC2 control without RvLEAMshort, only ~3% of ~1.7 million picked particles contributed to the final map; with RvLEAMshort, ~14% of ~2.5 million picked particles contributed, indicating substantially improved particle usability. | Real-world implementation / structural biology | Abe et al., 2024, Nature Communications | https://doi.org/10.1038/s41467-024-52091-1 | 2024-09 | (abe2024smallleaproteinsa pages 4-5) |
Table: This table compiles the main experimentally supported and inferred findings for RvLEAM from Ramazzottius varieornatus, including identity verification, mitochondrial localization, structural and biochemical properties, stress-tolerance effects, and recent biotechnology applications.
References
(tanaka2015novelmitochondriatargetedheatsoluble pages 2-4): Sae Tanaka, Junko Tanaka, Yoshihiro Miwa, Daiki D. Horikawa, Toshiaki Katayama, Kazuharu Arakawa, Atsushi Toyoda, Takeo Kubo, and Takekazu Kunieda. Novel mitochondria-targeted heat-soluble proteins identified in the anhydrobiotic tardigrade improve osmotic tolerance of human cells. PLoS ONE, 10:e0118272, Feb 2015. URL: https://doi.org/10.1371/journal.pone.0118272, doi:10.1371/journal.pone.0118272. This article has 143 citations and is from a peer-reviewed journal.
(tanaka2015novelmitochondriatargetedheatsoluble pages 5-7): Sae Tanaka, Junko Tanaka, Yoshihiro Miwa, Daiki D. Horikawa, Toshiaki Katayama, Kazuharu Arakawa, Atsushi Toyoda, Takeo Kubo, and Takekazu Kunieda. Novel mitochondria-targeted heat-soluble proteins identified in the anhydrobiotic tardigrade improve osmotic tolerance of human cells. PLoS ONE, 10:e0118272, Feb 2015. URL: https://doi.org/10.1371/journal.pone.0118272, doi:10.1371/journal.pone.0118272. This article has 143 citations and is from a peer-reviewed journal.
(hand2018challengesduringdiapause pages 8-8): Steven C. Hand, Daniel S. Moore, and Yuvraj Patil. Challenges during diapause and anhydrobiosis: mitochondrial bioenergetics and desiccation tolerance. IUBMB Life, 70:1251-1259, Oct 2018. URL: https://doi.org/10.1002/iub.1953, doi:10.1002/iub.1953. This article has 28 citations and is from a peer-reviewed journal.
(romeroperez2023whenphasedwithout pages 22-23): Paulette Sofia Romero-Perez, Yanniv Dorone, Eduardo Flores, Shahar Sukenik, and Steven Boeynaems. When phased without water: biophysics of cellular desiccation, from biomolecules to condensates. Chemical Reviews, 123:9010-9035, May 2023. URL: https://doi.org/10.1021/acs.chemrev.2c00659, doi:10.1021/acs.chemrev.2c00659. This article has 75 citations and is from a highest quality peer-reviewed journal.
(romeroperez2023whenphasedwithout pages 11-12): Paulette Sofia Romero-Perez, Yanniv Dorone, Eduardo Flores, Shahar Sukenik, and Steven Boeynaems. When phased without water: biophysics of cellular desiccation, from biomolecules to condensates. Chemical Reviews, 123:9010-9035, May 2023. URL: https://doi.org/10.1021/acs.chemrev.2c00659, doi:10.1021/acs.chemrev.2c00659. This article has 75 citations and is from a highest quality peer-reviewed journal.
(yoshida2022decipheringthebiological pages 4-6): Yuki Yoshida and Sae Tanaka. Deciphering the biological enigma—genomic evolution underlying anhydrobiosis in the phylum tardigrada and the chironomid polypedilum vanderplanki. Insects, 13:557, Jun 2022. URL: https://doi.org/10.3390/insects13060557, doi:10.3390/insects13060557. This article has 10 citations.
(schill2019environmentaladaptationsdesiccation pages 10-13): Ralph O. Schill and Steffen Hengherr. Environmental adaptations: desiccation tolerance. ArXiv, pages 273-293, Jan 2019. URL: https://doi.org/10.1007/978-3-319-95702-9_10, doi:10.1007/978-3-319-95702-9_10. This article has 50 citations.
(tanaka2015novelmitochondriatargetedheatsoluble pages 4-5): Sae Tanaka, Junko Tanaka, Yoshihiro Miwa, Daiki D. Horikawa, Toshiaki Katayama, Kazuharu Arakawa, Atsushi Toyoda, Takeo Kubo, and Takekazu Kunieda. Novel mitochondria-targeted heat-soluble proteins identified in the anhydrobiotic tardigrade improve osmotic tolerance of human cells. PLoS ONE, 10:e0118272, Feb 2015. URL: https://doi.org/10.1371/journal.pone.0118272, doi:10.1371/journal.pone.0118272. This article has 143 citations and is from a peer-reviewed journal.
(tanaka2015novelmitochondriatargetedheatsoluble media 470ae241): Sae Tanaka, Junko Tanaka, Yoshihiro Miwa, Daiki D. Horikawa, Toshiaki Katayama, Kazuharu Arakawa, Atsushi Toyoda, Takeo Kubo, and Takekazu Kunieda. Novel mitochondria-targeted heat-soluble proteins identified in the anhydrobiotic tardigrade improve osmotic tolerance of human cells. PLoS ONE, 10:e0118272, Feb 2015. URL: https://doi.org/10.1371/journal.pone.0118272, doi:10.1371/journal.pone.0118272. This article has 143 citations and is from a peer-reviewed journal.
(tanaka2015novelmitochondriatargetedheatsoluble pages 10-11): Sae Tanaka, Junko Tanaka, Yoshihiro Miwa, Daiki D. Horikawa, Toshiaki Katayama, Kazuharu Arakawa, Atsushi Toyoda, Takeo Kubo, and Takekazu Kunieda. Novel mitochondria-targeted heat-soluble proteins identified in the anhydrobiotic tardigrade improve osmotic tolerance of human cells. PLoS ONE, 10:e0118272, Feb 2015. URL: https://doi.org/10.1371/journal.pone.0118272, doi:10.1371/journal.pone.0118272. This article has 143 citations and is from a peer-reviewed journal.
(tanaka2015novelmitochondriatargetedheatsoluble media 129a06d0): Sae Tanaka, Junko Tanaka, Yoshihiro Miwa, Daiki D. Horikawa, Toshiaki Katayama, Kazuharu Arakawa, Atsushi Toyoda, Takeo Kubo, and Takekazu Kunieda. Novel mitochondria-targeted heat-soluble proteins identified in the anhydrobiotic tardigrade improve osmotic tolerance of human cells. PLoS ONE, 10:e0118272, Feb 2015. URL: https://doi.org/10.1371/journal.pone.0118272, doi:10.1371/journal.pone.0118272. This article has 143 citations and is from a peer-reviewed journal.
(abe2024smallleaproteinsa pages 2-3): Kaitlyn M. Abe, Gan Li, Qixiang He, Timothy Grant, and Ci Ji Lim. Small lea proteins mitigate air-water interface damage to fragile cryo-em samples during plunge freezing. Nature Communications, Sep 2024. URL: https://doi.org/10.1038/s41467-024-52091-1, doi:10.1038/s41467-024-52091-1. This article has 17 citations and is from a highest quality peer-reviewed journal.
(abe2024smallleaproteinsa pages 4-5): Kaitlyn M. Abe, Gan Li, Qixiang He, Timothy Grant, and Ci Ji Lim. Small lea proteins mitigate air-water interface damage to fragile cryo-em samples during plunge freezing. Nature Communications, Sep 2024. URL: https://doi.org/10.1038/s41467-024-52091-1, doi:10.1038/s41467-024-52091-1. This article has 17 citations and is from a highest quality peer-reviewed journal.
(abe2024smallleaproteinsa pages 5-6): Kaitlyn M. Abe, Gan Li, Qixiang He, Timothy Grant, and Ci Ji Lim. Small lea proteins mitigate air-water interface damage to fragile cryo-em samples during plunge freezing. Nature Communications, Sep 2024. URL: https://doi.org/10.1038/s41467-024-52091-1, doi:10.1038/s41467-024-52091-1. This article has 17 citations and is from a highest quality peer-reviewed journal.
(abe2024smallleaproteinsa pages 3-4): Kaitlyn M. Abe, Gan Li, Qixiang He, Timothy Grant, and Ci Ji Lim. Small lea proteins mitigate air-water interface damage to fragile cryo-em samples during plunge freezing. Nature Communications, Sep 2024. URL: https://doi.org/10.1038/s41467-024-52091-1, doi:10.1038/s41467-024-52091-1. This article has 17 citations and is from a highest quality peer-reviewed journal.
id: A0A0E4AVP3
gene_symbol: RvLEAM
product_type: PROTEIN
status: IN_PROGRESS
taxon:
id: NCBITaxon:947166
label: Ramazzottius varieornatus
description: >-
Group 3 late-embryogenesis abundant (LEA) protein targeted to the mitochondrial matrix
in the anhydrobiotic tardigrade Ramazzottius varieornatus. RvLEAM contains 9 LEA 11-mer
repeat motifs that form amphipathic helices under water-deficient conditions, acting as
a molecular shield to prevent undesirable protein aggregation and conformational changes
of lipid membranes. A predicted 31-residue mitochondrial transit peptide directs the
protein to the mitochondrial matrix. Heterologous expression in human cells improves
osmotic tolerance, consistent with a protective role during desiccation stress. RvLEAM
belongs to the LEA type 4 family, which is broadly conserved across plants, nematodes,
and other anhydrobiotic organisms.
existing_annotations:
- term:
id: GO:0005739
label: mitochondrion
evidence_type: IEA
original_reference_id: GO_REF:0000044
review:
summary: >-
Mitochondrial localization is strongly supported by multiple lines of evidence in
PMID:25675104. Immunohistochemistry confirmed mitochondrial localization in tardigrade
cells, and RvLEAM-GFP co-localized with MitoTracker Red in human cells. The IEA
annotation to the broad term 'mitochondrion' could be refined to 'mitochondrial
matrix' (GO:0005759) given that the protein is highly hydrophilic (GRAVY score -0.94,
no hydrophobic regions), which strongly suggests matrix rather than membrane
localization (PMID:25675104). UniProt annotates a mitochondrial transit peptide at
residues 1-31.
action: MODIFY
reason: >-
The annotation to GO:0005739 (mitochondrion) is correct but insufficiently specific.
RvLEAM has a predicted mitochondrial transit peptide (residues 1-31) and is highly
hydrophilic with no hydrophobic regions, strongly suggesting localization in the
mitochondrial matrix rather than the membrane. The more specific term GO:0005759
(mitochondrial matrix) is warranted based on both the experimental localization
data and biophysical properties of the protein.
proposed_replacement_terms:
- id: GO:0005759
label: mitochondrial matrix
additional_reference_ids:
- PMID:25675104
supported_by:
- reference_id: PMID:25675104
supporting_text: >-
RvLEAM is a group3 LEA protein and immunohistochemistry confirmed its
mitochondrial localization in tardigrade cells
- reference_id: PMID:25675104
supporting_text: >-
we identified two novel mitochondrial heat-soluble proteins, RvLEAM and MAHS
(Mitochondrial Abundant Heat Soluble), as potent mitochondrial protectants from
Ramazzottius varieornatus
- term:
id: GO:0009269
label: response to desiccation
evidence_type: IDA
original_reference_id: PMID:25675104
review:
summary: >-
RvLEAM is a group 3 LEA protein identified from the anhydrobiotic tardigrade
R. varieornatus (PMID:25675104). LEA proteins are well-established components of
the desiccation tolerance response in plants, nematodes, and other anhydrobiotic
organisms. The protein is described as having protective roles in water-deficient
environments, and its expression improves hyperosmotic tolerance of human cells.
UniProt annotates this protein with the keyword "Stress response" and describes
it as acting as a molecular shield in water-deficient conditions.
action: NEW
reason: >-
This is a core biological process annotation that is missing from GOA. RvLEAM is
a LEA protein involved in desiccation tolerance, and its expression improves
tolerance to water-deficient conditions. The response to desiccation annotation
captures the primary biological context of this protein.
additional_reference_ids:
- PMID:25675104
supported_by:
- reference_id: PMID:25675104
supporting_text: >-
Late Embryogenesis Abundant (LEA) proteins are heat-soluble proteins involved
in the desiccation tolerance of many anhydrobiotic organisms
- reference_id: PMID:25675104
supporting_text: >-
tardigrade mitochondria contain at least two types of heat-soluble proteins
that might have protective roles in water-deficient environments
- term:
id: GO:0006970
label: response to osmotic stress
evidence_type: IDA
original_reference_id: PMID:25675104
review:
summary: >-
Tanaka et al. (PMID:25675104) directly demonstrated that expression of RvLEAM
improved hyperosmotic tolerance of human HEp-2 cells. This provides direct
experimental evidence for a role in response to osmotic stress.
action: NEW
reason: >-
Direct experimental evidence from PMID:25675104 supports this annotation. RvLEAM
expression improved hyperosmotic tolerance in human cells, demonstrating the protein
functions in the cellular response to osmotic stress. This is the most directly
tested biological process for this protein.
additional_reference_ids:
- PMID:25675104
supported_by:
- reference_id: PMID:25675104
supporting_text: >-
we demonstrated that RvLEAM protein as well as MAHS protein improved the
hyperosmotic tolerance of human cells
- term:
id: GO:0051082
label: unfolded protein binding
evidence_type: IDA
original_reference_id: PMID:25675104
review:
summary: >-
LEA proteins are known to act as molecular shields that interact with other
macromolecules to prevent undesirable aggregation under water stress conditions.
While this implies interaction with proteins that may become aggregation-prone,
direct binding to unfolded proteins was not experimentally demonstrated for
RvLEAM specifically in PMID:25675104. The molecular shield mechanism is inferred
from the general LEA protein family literature. This annotation captures the
likely molecular function but should be considered provisional.
action: NEW
reason: >-
The molecular shield function of LEA proteins involves preventing protein aggregation
under stress, which is consistent with unfolded protein binding. However, this is
inferred from the general LEA protein literature rather than direct experimental
demonstration for RvLEAM. This annotation captures the likely molecular function
mechanism but should be considered provisional pending direct binding studies.
additional_reference_ids:
- PMID:25675104
supported_by:
- reference_id: PMID:25675104
supporting_text: >-
tardigrade mitochondria contain at least two types of heat-soluble proteins
that might have protective roles in water-deficient environments
references:
- id: GO_REF:0000044
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location
vocabulary mapping, accompanied by conservative changes to GO terms applied by
UniProt
findings: []
- id: PMID:25675104
title: >-
Novel mitochondria-targeted heat-soluble proteins identified in the anhydrobiotic
Tardigrade improve osmotic tolerance of human cells
findings:
- statement: RvLEAM is the first mitochondrial LEA protein identified in tardigrades
supporting_text: >-
we identified two novel mitochondrial heat-soluble proteins, RvLEAM and MAHS
(Mitochondrial Abundant Heat Soluble), as potent mitochondrial protectants from
Ramazzottius varieornatus
- statement: Immunohistochemistry confirmed mitochondrial localization in tardigrade cells
supporting_text: >-
RvLEAM is a group3 LEA protein and immunohistochemistry confirmed its
mitochondrial localization in tardigrade cells
- statement: Expression of RvLEAM improved hyperosmotic tolerance of human cells
supporting_text: >-
we demonstrated that RvLEAM protein as well as MAHS protein improved the
hyperosmotic tolerance of human cells
- statement: RvLEAM and MAHS have protective roles in water-deficient environments
supporting_text: >-
tardigrade mitochondria contain at least two types of heat-soluble proteins
that might have protective roles in water-deficient environments
- statement: LEA proteins are involved in desiccation tolerance
supporting_text: >-
Late Embryogenesis Abundant (LEA) proteins are heat-soluble proteins involved
in the desiccation tolerance of many anhydrobiotic organisms
- id: PMID:27649274
title: >-
Extremotolerant tardigrade genome and improved radiotolerance of human cultured
cells by tardigrade-unique protein
findings:
- statement: Genome sequencing of R. varieornatus (YOKOZUNA-1 strain)
core_functions:
- description: >-
RvLEAM is a group 3 LEA protein that acts as a molecular shield in the mitochondrial
matrix during water-deficient conditions. Its 9 LEA 11-mer repeat motifs form
amphipathic helices that interact with macromolecules to prevent aggregation
and protect lipid membranes. Expression in human cells improves osmotic tolerance
(PMID:25675104).
molecular_function:
id: GO:0051082
label: unfolded protein binding
locations:
- id: GO:0005759
label: mitochondrial matrix
directly_involved_in:
- id: GO:0009269
label: response to desiccation
supported_by:
- reference_id: PMID:25675104
supporting_text: >-
tardigrade mitochondria contain at least two types of heat-soluble proteins
that might have protective roles in water-deficient environments