Expression and Site-Directed Mutagenesis of the Lactococcal Abortive Phage Infection Protein AbiK
Bibliographic record
Abstract
Abortive infection mechanisms of Lactococcus lactis form a heterogeneous group of phage resistance systems that act after early phage gene expression. One of these systems, AbiK, aborts infection of the three most prevalent lactococcal phage groups of the dairy industry. In this study, it is demonstrated that the antiphage activity depends on the level of expression of the abiK gene and on the presence of a reverse transcriptase (RT) motif in AbiK. The abiK gene was shown to be part of an operon that includes two additional open reading frames, with one of these encoding a phage-related transcriptional repressor named Orf4. Expression of AbiK is driven by two promoters, PabiK and Porf3, the latter being repressed by Orf4 in vivo. Binding of the purified Orf4 to the Porf3 promoter was demonstrated in vitro by gel retardation assays. The N-terminal half of the deduced AbiK protein possesses an RT motif that was modified by site-directed mutagenesis. Conservative mutations in key positions resulted in the complete loss of the resistance phenotype. These data suggest that an RT activity might be involved in the phage resistance activity of AbiK. A model for the mode of action of AbiK is proposed.
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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".