# Dic4 ProtNLM2 function-description review

## Original prediction

> Mitochondrial transporter that mediates uptake of thiamine pyrophosphate (ThPP) into mitochondria

Original wording and all model/source metadata are retained in [Dic4-protnlm-source.json](Dic4-protnlm-source.json).

## Assessment

**UNC — mitochondrial thiamine pyrophosphate transport is unresolved.** Q9VVS1 is the native 302-residue Dic4-PA/PC product in FlyBase. The mitochondrial location is supported experimentally, but PMID:21130726 reports no detectable transport by reconstituted Dic4 in its dicarboxylate-carrier study. That finding establishes neither uptake nor exclusion of an untested substrate such as ThPP.

The prediction cites fungal Q59Q36 with a sequence-search score of 76.6 and a model score of 0.30. Mitochondrial carriers share architecture while differing markedly in transported substrates, as the Dic1/Dic3/Dic4 comparison itself demonstrates. No target-specific ThPP uptake assay or specificity-determining alignment establishes this transfer. The appropriate next experiment is reconstitution with labeled ThPP, validated protein incorporation and an active ThPP-carrier control.

Sources: [primary Dic4 study](https://doi.org/10.1016/j.bbabio.2010.11.013), [current UniProt record](https://www.uniprot.org/uniprotkb/Q9VVS1/entry), and the locally preserved FlyBase and donor records.