Oligomerization and negative autoregulation of the LysR-type transcriptional regulator HsdR from Comamonas testosteroni

► 3α-Hydroxysteroid dehydrogenase (3α-HSD/CR) initiates steroid degradation in Comamonas testosteroni. ► The gene coding for 3α-HSD/CR, hsdA, is regulated by multiple factors including HsdR. ► HsdR belongs to the LysR-type transcriptional regulator (LTTR) family. ► Interestingly, HsdR is active as an oligomer in the regulation of hsdA expression. ► Further, HsdR negatively regulates its own expression.