Identification and Characterization of Binding Sites on S100A7, a Participant in Cancer and Inflammation Pathways
Bibliographic record
Abstract
S100A7 (psoriasin) is a member of the S100 family of signaling proteins. It is implicated in and considered a therapeutic target for inflammation and cancer, yet no small molecule ligands for S100A7 have been identified. To begin the development of specific small molecule inhibitors of S100A7 function, we have used a series of surface binding fluorescent dyes to probe the surface hydrophobic sites. Two naphthalene-based dyes (2,6-ANS and 1,8-ANS) were found to bind S100A7 in a distinct cleft. We characterized the binding interaction by determining both the structure of S100A7 bound to 2,6-ANS and the structure of S100A7 bound to 1,8-ANS to 1.6 A. In both cases, two molecules of dye were docked such that the naphthalene groups were positioned in two symmetry-related grooves that are formed by the N-terminal helices of each monomer. We observed that Met12 acts as a gatekeeper to the binding cleft, adopting an "open" conformation for the more elongated 2,6-ANS while remaining in a "closed" conformation for the more compact 1,8-ANS. Steady-state fluorescence experiments revealed that S100A7 binds two copies of 2,6-ANS, each with a K(d) of 125 muM. Time-resolved fluorescence lifetime measurements indicated that the two molecules of 2,6-ANS bind in two independent binding sites with different fluorescence lifetimes, suggesting that the S100A7 homodimer is not perfectly symmetric in solution. Isothermal titration calorimetry studies demonstrate that S100A7 has a higher affinity for 2,6-ANS than 1,8-ANS. Yeast two-hybrid studies were also used to probe contributions of individual residues of an S100A7 triple mutant with respect to Jab1 binding. Mutation of Leu78, which forms part of the Met12 cleft occupied by 2,6-ANS, reduced the level of Jab1 binding, suggesting a potentially important role for the Met12 hydrophobic pocket in defining a Jab1 interface. Additional Y2H studies also delineate contributions of Gln88 and in particular Asp56 that shows the most significant abrogated binding to Jab1. Collectively, these data suggest a complex interaction between S100A7 and the much larger Jab1. These studies form the basis for the development of small molecule reporters and modifiers of S100A7 form and function.
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How this classification was reachedexpand
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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".