The “Second Stalk” of <i>Escherichia</i> <i>coli</i> ATP Synthase: Structure of the Isolated Dimerization Domain<sup>,</sup>
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Bibliographic record
Abstract
The b subunit of E. coli F(0)F(1)-ATPase links the peripheral F(1) subunits to the membrane-integral F(0) portion and functions as a "stator", preventing rotation of F(1). The b subunit is present as a dimer in ATP synthase, and residues 62-122 are required to mediate dimerization. To understand how the b subunit dimer is formed, we have studied the structure of the isolated dimerization domain, b(62-122). Analytical ultracentrifugation and solution small-angle X-ray scattering (SAXS) indicate that the b(62-122) dimer is extremely elongated, with a frictional ratio of 1.60, a maximal dimension of 95 A, and a radius of gyration of 27 A, values that are consistent with an alpha-helical coiled-coil structure. The crystal structure of b(62-122) has been solved and refined to 1.55 A. The protein crystallized as an isolated, monomeric alpha helix with a length of 90 A. Combining the crystal structure of monomeric b(62-122) with SAXS data from the dimer in solution, we have constructed a model for the b(62-122) dimer in which the two helices form a coiled coil with a right-handed superhelical twist. Analysis of b sequences from E. coli and other prokaryotes indicates conservation of an undecad repeat, which is characteristic of a right-handed coiled coil and consistent with our structural model. Mutation of residue Arg-83, which interrupts the undecad pattern, to alanine markedly stabilized the dimer, as expected for the proposed two-stranded, right-handed coiled-coil structure.
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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 | 0.001 | 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