Hyp-1 protein from St John’s wort as a PR-10 protein

PR-10 proteins form a large subclass of plant pathogenesis-related proteins that are expressed in response to harmful

environmental factors in a wide range of species. Although their function is still not clear, structural data suggest

that their characteristic internal hydrophobic cavity can bind relevant plant small-molecule mediators. Hyp-1 from

St John's wort (Hypericum perforatum ), initially proposed as a catalyst for the biosynthesis of hypericin, was

eventually shown to share sequence similarity and a folding pattern with PR-10 proteins. The crystal structure of

Hyp-1 in complex with fluorescent probe ANS reveals three distinct and separated binding sites that are unique

among PR-10 proteins. The structure can provide guidance in our quest for the true physiological ligands of Hyp-1.