The molecular mechanism of the type IVa pilus motors
Bibliographic record
Abstract
ABSTRACT Type IVa pili are protein filaments essential for virulence in many bacterial pathogens; they extend and retract from the surface of bacterial cells to pull the bacteria forward with unprecedented force. They are used for attachment, swarming and twitching motility, biofilm formation, up-regulation of other virulence factors, and natural competence. The pilus is assembled by the motor subcomplex which consists of the inner membrane protein PilC and the cytoplasmic ATPase PilB. How PilB catalyzes this process is unknown, due in part to the lack of high-resolution structural information. Phylogenetic analysis of PilB-like ATPases, including GspE, PilT, BfpD, FlaI, and archaeal GspE2 revealed highly conserved residues essential for function in this family of ATPases. Here we report the structure of the core ATPase domains of Geobacter metalloreducens PilB bound to ADP and the non-hydrolysable ATP analogue, AMPPNP, at 3.4 and 2.3Å, respectively. Importantly, these structures were determined in non-saturating nucleotide conditions, revealing important differences in nucleotide binding between chains. Analysis of these differences revealed the sequential turnover of nucleotide by the chains, and the corresponding domain movements. Our data indicate a clockwise rotation of movement in PilB, which would support the assembly of a right-handed helical pilus. Conversely, our analysis suggests a counterclockwise rotation in PilT that would enable right-handed pilus disassembly. The proposed model provides insight into how this family of ATPases can power pilus extension and retraction with extraordinary forces.
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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 | 0.000 |
| 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".