Determinants of oligomerization of the bifunctional protein DCoHalpha and the effect on its enzymatic and transcriptional coactivator activities.

DCoH and DCoHalpha are bifunctional proteins that function as 4a-hydroxytetrahydrobiopterin dehydratases and as coactivators of HNF1alpha-dependent transcription. Although these isoforms share sequence and structural similarity and equivalent enzyme activities, DCoH is a hyperstable tetramer whereas DCoHalpha readily forms dimers. Differences in quaternary structure affect the formation of the DCoH(alpha):HNF1alpha complex.