The characteristics and roles of TamR, a MarR family transcriptional regulator from Streptomyces coelicolor

Abstract

Multiple antibiotic resistance regulator (MarR) family transcriptional regulators usually play their regulatory role by responding to specific ligands. In this study, TamR (trans‐aconitate methyltransferase regulator), a member of the MarR family transcriptional regulators from Streptomyces coelicolor was investigated in order to understand its characteristics and its roles. After the tamR gene was cloned from the genomic DNA of S. coelicolor and introduced into E. coli, TamR was overexpressed and purified to apparent homogeneity. Gel filtration, cross‐linking, EMSA, fluorescence quenching and other experiments were used to investigate its characteristics and roles. The results show that TamR exists as dimer. A divergently oriented adjacent gene tam, which encodes trans‐aconitate methyltransferase is regulated by TamR. TamR binds with high affinity to the intergenic region between the tamR and tam genes, a genomic region that covers the promoter region of both genes and forms two different DNA‐protein complexes. Trans‐aconitic acid can attenuate the binding of TamR with DNA. In addition, other chemical compounds related to the citrate isomerization step in citric acid cycle, which include cis‐aconitic acid, citric acid and isocitrate, can also attenuate the interaction of TamR with DNA. A proposed model of TamR regulation is presented in order to explain the possible roles of TamR in S. coelicolor.