Structure-function analysis of a mitochondrial cell death protein, Bcl-2/E1B 19K interacting protein 3 (BNip3)
Bibliographic record
Abstract
BNip3 resembles Bcl-2-related proteins, based on sequence similarity to the Bcl-2 homology 3 (BH3) domain and COON-terminal transmembrane (TM) domain. Characteristically, the 'BH3-only' class of Bcl-2 proteins heterodimerize with Bcl-2/Bcl-xL and induce cell death through their BH3 domain. BNip3 and its 'C. elegans' orthologue, CeBNip3 interact with cell death repressors Bcl-2, Bcl-xL and CED-9 in yeast and mammalian expression systems. Unlike other BH3-only agonists, deletion mapping of BNip3 excluded its putative BH3 domain and identified the NH 2-terminus and TM domain critical for Bcl-2 heterodimerization, and either region sufficient for Bcl-xL interaction. Similar mapping studies of CeBNip3 demonstrated its association with CED-9 and Bcl-xL exclusively through its TM domain. Both BNip3 and CeBNip3 induce cell death in several cell lines. Yet, the removal of the BH3-like domain in either protein does not diminish its cytotoxicity. Some Bcl-2 homologues form homodimers through regions of shared homologyto regulate their functio . Following 'in vitro' transcription/translation, BNip3 was expressed primarily as a 60 kDa protein along with a 30 kDa product. Interaction of BNip3 monomers was observed in the yeast two-hybrid system and deletion mapping localized the region mediating homodimerization to the TM domain. The BNip3 TM domain is also critical for mitochondria) targeting and cell death function. Its removal results in cytosolic expression and eliminates both its homologous interaction and cytotoxicity. Several BNip3 TM domain mutations were found to disrupt SDS-resistant BNip3 homodimerization, but did not interfere with its mitochondria) localization or killing activity. The substitution of the BNip3 TM domain with cytochrome ' b5' targeting sequence directed protein expression to nonmitochondrial sites, promoting both cell death and Bcl-2/Bcl-xL heterodimerization. Therefore, the function of BNip3 is independent of homodimerization, but the TM domain is necessary for mitochondria) targeting and cell death function. In conclusion, BNip3 is a mitochondria) cell death-inducing protein, which although structurally related to the Bcl-2 family appears to heterodimerize and to induce cell death in the absence of its BH3-like domain. Thus, BNip3-related proteins define a new class of cell death proteins, which interact with Bcl-2, Bcl-xL and CED-9 and kill independent of a BH3 domain.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".