# WFS1 Wolframin — H323R Variant Card

**Molecular Atlas Pilot · RareResearch.AI · Generated by wolfram-variant-card skill**

*Histidine-to-arginine swap inside transmembrane helix TM1 — partial-charge histidine replaced by full-charge arginine in the bilayer environment, with mild predicted DeltaDeltaG that does not capture the membrane desolvation penalty.*

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## Identity

| Field | Value |
|---|---|
| **Variant** | H323R (p.Histidine323Arginine) |
| **DNA change** | c.968A>G |
| **Gene · Protein** | WFS1 · Wolframin (890 aa) |
| **UniProt** | O76024 · WFS1_HUMAN |
| **ClinVar accession** | VCV000872210 |
| **Amino acid change** | Histidine (imidazole side chain, pKa ~6.0, mostly neutral at physiological pH but partially protonated) to Arginine (large, fully positively charged guanidinium, pKa ~12.5, ionized everywhere in physiological range) at position 323. The substitution converts a conditionally polar residue into a permanently charged one. |

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## Structural Context

| Field | Value |
|---|---|
| **AlphaFold model** | AF-O76024-F1, v6 |
| **pLDDT at residue 323** | **76.94** — well-folded |
| **Domain** | TM1 (314-334), helical transmembrane |
| **Position context** | Position 323 sits inside transmembrane helix TM1 (residues 314-334) — wolframin's first membrane-spanning segment, embedded in the ER bilayer. pLDDT 76.94 places the residue in an ordered region with confidence. |
| **IDR flag** | No — pLDDT above 50 threshold |

**UniProt features at this position:**

  - Chain: 1-890 Wolframin
  - Transmembrane: 314-334 Helical

> H323 is held between His322 (2.45 Angstrom) and Ile324 (2.46 Angstrom) covalently. Through-space neighbors read Pro320 (3.53 Angstrom), Ala326 (4.25 Angstrom), Thr321 (4.49 Angstrom), Asn325 (4.49 Angstrom), and Leu327 (4.93 Angstrom). The pair of adjacent histidines at 322-323 is structurally distinctive: two imidazole side chains separated by a single peptide bond, both within a transmembrane helix. The wild-type arrangement likely places both imidazoles facing inward toward each other or coordinating with the polar Thr321 and Asn325, forming a small polar cluster within the helix interior.

Replacing H323 with arginine introduces a fully charged guanidinium where a partial-charge imidazole sat. The thermodynamic problem is desolvation: arginine in a bilayer interior carries a desolvation cost of 8-12 kcal/mol if fully buried, less if its side chain can snorkel toward an interfacial water network. The presence of nearby polar residues (Thr321, Asn325, the H322 imidazole) provides some partial solvation, but the local geometry was not built to host a permanently charged residue.

The structural consequence is one of two outcomes: either Arg323's guanidinium snorkels toward the cytoplasmic face of TM1 (potentially dragging the helix slightly out of register), or it remains buried at substantial energetic cost. Either outcome perturbs TM1 packing against its neighboring helices.

DynaMut2's DeltaDeltaG of -0.02 kcal/mol — essentially zero — is a known weakness of energy functions for buried charge substitutions. The function captures local van der Waals and hydrogen-bond changes but under-weights desolvation. AlphaMissense at 0.687 is closer to a true read of the disruption: clearly pathogenic (above the 0.564 threshold) but not the highest-scoring variant in this batch, consistent with the imidazole-to-guanidinium swap being chemically less drastic than e.g. a glycine-to-arginine substitution.

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## Computational Predictions

### AlphaMissense
| Field | Value |
|---|---|
| am_pathogenicity | **0.6869** |
| am_class | **LPath** |
| Interpretation | Likely pathogenic (threshold 0.564) |

### DynaMut2
| Field | Value |
|---|---|
| ΔΔG (kcal/mol) | **-0.02 (Destabilising)** |
| Job ID | 177991408145 |
| Result URL | https://biosig.lab.uq.edu.au/dynamut2/results_prediction/177991408145 |

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## Clinical Evidence

| Field | Value |
|---|---|
| Classification | **Pathogenic/Likely pathogenic** |
| Review status | criteria provided, multiple submitters, no conflicts |
| Last evaluated | 2020/01/01 00:00 |
| Inheritance | Inheritance pattern not explicitly recorded; ClinVar P/LP review provided. |
| WFS1 variant landscape | H323R is 1 of ~326 pathogenic-spectrum variants in WFS1 (out of 2,243 catalogued in ClinVar) |

- Optic atrophy

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## Research Path Decision Tree

```
ΔΔG < 2  + binding site affected   →  CATEGORY 3 — docking experiments
ΔΔG 2–4                            →  CATEGORY 2 — pharmacological chaperones
ΔΔG > 4                            →  CATEGORY 1 — gene therapy
pLDDT < 50                         →  CATEGORY 5 — IDR, experimental only
Stable fold + functional site hit  →  CATEGORY 4 — site-specific docking
```

## Final Schema Categorization

**Category 3/4 — Most Druggable**

Final classification: Category 3 — Most Druggable, with explicit caveats. The schema's strict DeltaDeltaG-magnitude rule places H323R in the small-perturbation bucket; the chemistry argues for a slightly more serious read. The variant is well-modeled (pLDDT 76.94), the AlphaMissense score is solidly pathogenic (0.687), and the lesion is localized.

For druggability, the residue is buried in TM1 — accessible only via the bilayer or by a small molecule that engages the helix from the interfacial surface. Pharmacological chaperones that stabilize TM1 packing during co-translational membrane insertion are the most plausible therapeutic route. The clinical phenotype is currently limited to optic atrophy in ClinVar, which may reflect incomplete phenotypic ascertainment rather than tissue-specific penetrance.

**Why this card matters.** H323R highlights the same TM-charge-burial issue as G437R: energy functions trained on soluble-protein mutations consistently under-read the cost of introducing a charged residue into a lipid bilayer. The Atlas should treat all such variants (any TM-resident histidine-to-arginine, glutamate-to-lysine, etc.) with an automatic structural-chemistry override flag.

For wolframin specifically, mapping the TM-helix charged-residue substitutions is high-leverage. Each TM helix has a small number of residues whose substitution introduces or alters charge in the bilayer; these are systematically under-scored by DynaMut2 but well-flagged by AlphaMissense. The dual-metric framing the Atlas uses is exactly the right tool for catching them.

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## Files in this folder

- `AF-O76024-F1-model_v6.pdb` — AlphaFold structure
- `H323R_molstar_viewer.html` — interactive 3D viewer (auto-highlights position 323 with ball-and-stick + neighbors within 5Å)
- `H323R_variant_card.md` — this card (source of truth)
- `H323R_variant_card.html` — styled printable card
- `H323R_dynamut2_summary.html` — clean offline DynaMut2 result card
- `dynamut2_result.json` — structured result data
- `dynamut2_result_page.html` — local snapshot of the Biosig result page (asset URLs absolutized)
- `H323R_wildtype_interactions.pse` / `H323R_mutant_interactions.pse` — PyMOL sessions

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*Generated by wolfram-variant-card skill · RareResearch.AI Molecular Atlas*
*Every assumption documented. Every score sourced.*