Structural analysis of the carboxy terminal PH domain of pleckstrin bound to D-myo-inositol 1,2,3,5,6-pentakisphosphate
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Bibliographic record
Abstract
BACKGROUND: Pleckstrin homology (PH) domains are one of the most prevalent domains in the human proteome and represent the major phosphoinositide-binding module. These domains are often found in signaling proteins and function predominately by targeting their host proteins to the cell membrane. Inositol phosphates, which are structurally similar to phosphoinositides, are not only known to play a role as signaling molecules but are also capable of being bound by PH domains. RESULTS: In the work presented here it is shown that the addition of commercial myo-inositol hexakisphosphate (IP6) inhibited the binding of the carboxy terminal PH domain of pleckstrin (C-PH) to phosphatidylinositol 3,4-bisphosphate with an IC50 of 7.5 muM. In an attempt to characterize this binding structurally, C-PH was crystallized in the presence of IP6 and the structure was determined to 1.35 A. Examination of the resulting electron density unexpectedly revealed the bound ligand to be D-myo-inositol 1,2,3,5,6-pentakisphosphate. CONCLUSION: The discovery of D-myo-inositol 1,2,3,5,6-pentakisphosphate in the crystal structure suggests that the inhibitory effects observed in the binding studies may be due to this ligand rather than IP6. Analysis of the protein-ligand interaction demonstrated that this myo-inositol pentakisphosphate isomer interacts specifically with protein residues known to be involved in phosphoinositide binding. In addition to this, a structural alignment of other PH domains bound to inositol phosphates containing either four or five phosphate groups revealed that the majority of phosphate groups occupy conserved locations in the binding pockets of PH domains. These findings, taken together with other recently reported studies suggest that myo-inositol pentakisphosphates could act to regulate PH domain-phosphoinositide interactions by directly competing for binding, thus playing an important role as signaling molecules.
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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 | 0.001 |
| 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