<i>Tomato Ringspot Virus</i> Proteins Containing the Nucleoside Triphosphate Binding Domain Are Transmembrane Proteins That Associate with the Endoplasmic Reticulum and Cofractionate with Replication Complexes
Bibliographic record
Abstract
Replication of all known positive-strand RNA viruses occurs in replication complexes associated with intracellular membranes. The putative nucleoside triphosphate binding (NTB) protein of Tomato ringspot virus (ToRSV) contains a stretch of hydrophobic residues at its C terminus, suggesting that it may act as a membrane anchor for the replication complex. Anti-NTB antibodies detected two predominant proteins in membrane-enriched fractions (the 66-kDa NTB and 69-kDa NTB-VPg proteins) along with other, larger proteins. The proteins containing the NTB domain cofractionated with markers of the endoplasmic reticulum (ER) and with ToRSV-specific RNA-dependent RNA polymerase activity in sucrose gradients. ToRSV infection induced severe changes in the morphology of the ER in plants expressing an ER-targeted green fluorescent protein (ER-GFP), and proteins containing the NTB domain colocalized with ER-GFP in indirect immunofluorescence assays. The proteins containing the NTB domain have properties of integral membrane proteins. Proteinase K protection assays using purified membranes from infected plants revealed that although the central portion of the NTB domain is exposed to the cytoplasmic face of the membranes, an 8-kDa fragment, recognized by anti-VPg antibodies, is protected by the membranes. This fragment probably consists of the 3-kDa VPg and the 5-kDa stretch of hydrophobic residues at the C terminus of the NTB protein, suggesting a luminal location for the VPg in at least a portion of the molecules. These results provide evidence that proteins containing the NTB domain are transmembrane proteins associated with ER-derived membranes and support the hypothesis that one or several of the proteins containing the NTB domain anchor the replication complex to the ER.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".