Autoregulation of hpdR and its effect on CDA biosynthesis in Streptomyces coelicolor

HpdR, an IcIR-family regulator in Streptomyces coelicolor, is a substrate-dependent repressor for the tyrosine catabolic gene hppD. In this study, Si nuclease protection assays revealed that hpdR is subject to a negative autoregulation. Purified HpdR showed specific DNA-binding activity for the promoter region of hpdR, indicating that the autoregulation of hpdR is performed directly. The disruption of hpdR led to reduced production of CDA by S. coelicolor J1501, suggesting a positive effect of hpdR on CDA biosynthesis. Electrophoretic mobility shift assays showed that HpdR specifically bound to the promoter region of hmaS (SCO3229 in the CDA gene cluster), encoding 4-hydroxymandelic acid synthase. Disruption of hmaS in 11501 abolished CDA production. It is possible that hpdR regulates CDA biosynthesis by controlling the transcription of hmaS.