Increase in Xylanase Production by <i>Streptomyces lividans</i> through Simultaneous Use of the Sec- and Tat-Dependent Protein Export Systems
Why this work is in the frame
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Bibliographic record
Abstract
Xylanase B1 (XlnB1) from Streptomyces lividans is a protein consisting of two discrete structural and functional units, an N-terminal catalytic domain and a C-terminal substrate binding domain. In the culture medium, two forms of xylanase B are present, namely, XlnB1 and XlnB2, the latter of which corresponds to the catalytic domain of XlnB1 deprived of the substrate binding domain. Both forms of the xylanase have the same activity on xylan. The enzyme is secreted through the Sec-dependent pathway with a better yield of XlnB1 than XlnB2. Interestingly, XlnB2 exhibits 80% identity with XlnC which is secreted exclusively through the Tat-dependent pathway. To demonstrate whether XlnB1 and XlnB2 could also be secreted through the Tat-dependent pathway, the Tat-targeting xlnC signal sequence was fused to the structural genes of xlnB1 and xlnB2. Both XlnB1 and XlnB2 were secreted through the Tat-dependent pathway, but XlnB2 was better produced than XlnB1. As XlnB1 and XlnB2 could be better secreted through the Sec- and Tat-dependent systems, respectively, a copy of the structural gene of xlnB1 fused to a Sec signal sequence and a copy of the structural gene of xlnB2 fused to a Tat signal sequence were inserted into the same plasmid under the control of the xlnA promoter. The transformant produced xylanase activity which corresponded approximately to the sum of activities of the individual strain producing xylanase by either the Sec- or Tat-dependent secretion system. This indicated that both secretion systems are functional and independent of each other in the recombinant strain. This is the first report on the efficient secretion of a protein using two different secretion systems at the same time. Assuming that the protein to be secreted could be properly folded prior to and after translocation via the Tat- and Sec-dependent pathways, respectively, the simultaneous use of the Sec- and Tat-dependent pathways provides an efficient means to increase the production of a given protein.
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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 | 0.000 | 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 | 0.000 |
| 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 it