Crystal Structure of the Transcriptional Regulator Rv0678 of Mycobacterium tuberculosis

• Published in: The Journal of biological chemistry 2014-06, Vol.289 (23), p.16526-16540
• Main Authors: Radhakrishnan, Abhijith, Kumar, Nitin, Wright, Catherine C., Chou, Tsung-Han, Tringides, Marios L., Bolla, Jani Reddy, Lei, Hsiang-Ting, Rajashankar, Kanagalaghatta R., Su, Chih-Chia, Purdy, Georgiana E., Yu, Edward W.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Bacterial Transcription; Base Sequence; Crystal Structure; Crystallography, X-Ray; Dimerization; DNA Primers; Fatty Acid Transport; Infectious Diseases; MarR Family Regulators; Molecular Sequence Data; Mycobacterial Membrane Protein Large; Mycobacterial Membrane Protein Small; Mycobacterium tuberculosis; Mycobacterium tuberculosis - chemistry; Mycobacterium tuberculosis - metabolism; Polymerase Chain Reaction; Protein Structure and Folding; Rv0678; Sequence Homology, Amino Acid; Transcriptional Regulation
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.538959

Recent work demonstrates that the MmpL (mycobacterial membrane protein large) transporters are dedicated to the export of mycobacterial lipids for cell wall biosynthesis. An MmpL transporter frequently works with an accessory protein, belonging to the MmpS (mycobacterial membrane protein small) family, to transport these key virulence factors. One such efflux system in Mycobacterium tuberculosis is the MmpS5-MmpL5 transporter. The expression of MmpS5-MmpL5 is controlled by the MarR-like transcriptional regulator Rv0678, whose open reading frame is located downstream of the mmpS5-mmpL5 operon. To elucidate the structural basis of Rv0678 regulation, we have determined the crystal structure of this regulator, to 1.64 Å resolution, revealing a dimeric two-domain molecule with an architecture similar to members of the MarR family of transcriptional regulators. Rv0678 is distinct from other MarR regulators in that its DNA-binding and dimerization domains are clustered together. These two domains seemingly cooperate to bind an inducing ligand that we identified as 2-stearoylglycerol, which is a fatty acid glycerol ester. The structure also suggests that the conformational change leading to substrate-mediated derepression is primarily caused by a rigid body rotational motion of the entire DNA-binding domain of the regulator toward the dimerization domain. This movement results in a conformational state that is incompatible with DNA binding. We demonstrate using electrophoretic mobility shift assays that Rv0678 binds to the mmpS5-mmpL5, mmpS4-mmpL4, and the mmpS2-mmpL2 promoters. Binding by Rv0678 was reversed upon the addition of the ligand. These findings provide new insight into the mechanisms of gene regulation in the MarR family of regulators. The expression of the Mycobacterium tuberculosis MmpS5-MmpL5 transporter is controlled by the MarR-like transcriptional regulator Rv0678. Rv0678 forms a dimeric two-domain molecule with the architecture similar to members of the MarR family of transcriptional regulators. Rv0678 is distinct in that its DNA-binding and dimerization domains cooperate to bind an inducing ligand. These findings suggest a mechanism for ligand and regulator derepression.