# Spcs2 re-review: A0A140LHW5 versus canonical Q9CYN2

Generated by `compare_sequences_rereview.py` (UniProt REST + Ensembl REST, live fetch).

## Sequence comparison

- A0A140LHW5 length: 74 aa
- Q9CYN2 length: 226 aa
- Identical N-terminal prefix: residues 1-66
- A0A140LHW5 divergent tail (67-74): `KRPHRNGS`
- Q9CYN2 residues from 67: `VLLEKYKYVENFGLIDGRLT...`
- Tail occurs as a substring of Q9CYN2: False

## Canonical Q9CYN2 features relative to the shared prefix

| Feature | Description | Start | End | Inside shared prefix |
|---|---|---|---|---|
| Chain | Signal peptidase complex subunit 2 | 2 | 226 | partial |
| Topological domain | Cytoplasmic | 2 | 86 | partial |
| Transmembrane | Helical | 87 | 107 | no |
| Topological domain | Lumenal | 108 | 111 | no |
| Transmembrane | Helical | 112 | 132 | no |
| Topological domain | Cytoplasmic | 133 | 226 | no |
| Modified residue | N-acetylalanine | 2 | 2 | yes |
| Modified residue | N6-acetyllysine | 169 | 169 | no |
| Modified residue | N6-acetyllysine | 191 | 191 | no |

## Transcript models (Ensembl)

- benchmark ENSMUST00000208465 (Spcs2-206), biotype protein_coding, is_canonical=0, 4 exons, translation ENSMUSP00000146574 length 74, strand -1
- canonical ENSMUST00000036274 (Spcs2-201), biotype protein_coding, is_canonical=1, 5 exons, translation ENSMUSP00000041152 length 226, strand -1

| Canonical exon | Start | End | Length (nt) | Present in benchmark | Length mod 3 |
|---|---|---|---|---|---|
| ENSMUSE00001379486 | 99507971 | 99508184 | 214 | True | 1 |
| ENSMUSE00000263826 | 99498183 | 99498266 | 84 | True | 0 |
| ENSMUSE00000263814 | 99497506 | 99497666 | 161 | False | 2 |
| ENSMUSE00000263809 | 99493907 | 99494041 | 135 | True | 0 |
| ENSMUSE00000402725 | 99486776 | 99489090 | 2315 | True | 2 |

A skipped internal coding exon whose length is not a multiple of 3 shifts the
reading frame of all downstream codons; the divergent tail then reflects
out-of-frame translation of the next exon until a stop codon is met.