- Fold
- Predicted single-pass membrane protein — consistent with the reported type II ER-membrane topology: a cytoplasmic N-terminus, one TM anchor (43–63), and a lumenal GNAT catalytic domain.
- Active-Site Region
- AstraBIND unclassified hypothesis (confidence 0.738) — a residue-level, substrate/cofactor-facing starting point for docking / mutagenesis; no validated ligand.
- Clean Signal
- One aggregation-prone segment flagged (AstraUNFOLD amyloid max 0.531) — worth screening in construct design.
Model-reported confidence for the headline calls (amber = the load-bearing prediction the rest of the profile builds on). These are model-estimated probabilities that rank and gate each call — not calibrated rates of experimental success.
The Gap
Why This Target Is Still Dark
Most tractable enzyme families have been structurally explored. NAT8 (N-acetyltransferase 8) has not: an IDG Tbio target with no experimental structure in the PDB and only a handful of functional studies. It is an ER-membrane-anchored, acetyl-CoA-dependent acetyltransferase with two reported jobs — N6-acetylating lysines on lumenal proteins such as PROM1 and BACE1, and acetylating cysteine S-conjugates to form mercapturic acids, the final, excretable step in detoxifying reactive electrophiles. Interest is real: NAT8 variants are among the more reproducible GWAS hits for kidney function and circulating N-acetylated amino-acid levels — but there is almost nothing structural to look up.
That combination — genuine interest, near-zero structural information — is where prediction earns its keep: everything below is computed from the canonical 227-residue sequence with Orbion's Astra suite, with no experimental NAT8 structure used as input. For a target this dark, there is no structure to consult.
Architecture & Topology
How the Sequence Is Organised
| Element | Residues | Note |
|---|---|---|
| Transmembrane Helices | 1 predicted | Boundaries: 43–63. |
| N-Acetyltransferase | 61–220 | UniProt-annotated domain. |
The Predicted Pocket
The Predicted Active-Site Region
A residue-level hypothesis from AstraBIND. NAT8 has no ligand-bound relative for AstraBIND to retrieve from, so this is a structure-based cavity prediction rather than a retrieval-grounded one — but every predicted residue falls within the GNAT N-acetyltransferase domain (61–220), the acetyl-CoA / substrate-facing region, so it is at least domain-consistent. Treat it as a domain-level starting point for mutagenesis, not a validated pocket.
Site: Predicted substrate / cofactor-facing residues
Post-Translational & Structural Features
Specific, Testable Residues
- N-acetyltransferase (61–220) — the UniProt-annotated GNAT catalytic domain that carries the predicted acetyl-CoA / substrate-facing active site.
- Aggregation-prone segment flagged (AstraUNFOLD amyloid max 0.531) — a short hydrophobic stretch worth screening or engineering out when designing a soluble construct.
Recommended Experimental Follow-Up
An Orphan Sequence, Turned Into a Ranked Plan
Each prediction is paired with the experiment that would test it and the readout to watch for.
| Prediction | Experiment | Readout |
|---|---|---|
| Active-Site Region Residues | Alanine scan at the predicted site + N-acetyltransferase assay (acetyl-CoA donor; cysteine-S-conjugate or lysine acceptor) | Loss of acetyl-transfer activity at the predicted site |
| Disordered / Flexible Regions | Fusion-partner insertion or terminal truncation | Improved expression / thermostability for structural work |
| Predicted Type II Membrane Topology | Protease-protection / membrane-fractionation assay | Confirm the single-pass, lumenal-domain ER topology |
Scope & Limitations
What This Is — and Isn't
- Prediction, not experiment. These are computational hypotheses to prioritise experiments — not a structure or an assay. Nothing here is wet-lab validated.
- The pocket is predicted; the ligand is not named. AstraBIND is retrieval-based; the honest output is a residue-level hypothesis, not a proven druggable site or a validated binder.
- Genetic association, not mechanism. NAT8's kidney rationale comes from GWAS — variants at the locus track with kidney function, CKD progression and N-acetylated amino-acid levels — not from a demonstrated causal pathway, and there is no Mendelian NAT8 disease. Its two reported activities (mercapturic-acid formation and ER-lumen lysine acetylation of PROM1 / BACE1) are biochemically supported, but the line from enzyme to renal phenotype is unproven. Treat the disease link as a hypothesis.
All predictions were generated with Orbion's Astra suite from the canonical NAT8 sequence (UniProt Q9UHE5), using AlphaFold-derived structural features. Reported values are model outputs; model internals are out of scope.
References
- [1]UniProt Consortium. UniProtKB entry Q9UHE5 (NAT8, human). uniprot.org.
- [2]Pharos (Illuminating the Druggable Genome). NAT8 target record — Tbio. pharos.nih.gov.
- [3]Veiga-da-Cunha M et al. Molecular identification of NAT8 as the enzyme that acetylates cysteine S-conjugates to mercapturic acids. (2010). https://doi.org/10.1074/jbc.m110.110924
- [4]Luo S et al. NAT8 Variants, N-Acetylated Amino Acids, and Progression of CKD. (2020). https://doi.org/10.2215/cjn.08600520
- [5]Rigby MJ et al. The endoplasmic reticulum acetyltransferases ATase1/NAT8B and ATase2/NAT8 are differentially regulated to adjust engagement of the secretory pathway. (2020). https://doi.org/10.1111/jnc.14958