Crystal structure of TM1030 from Thermotoga maritima at 2.3 Å resolution reveals molecular details of its transcription repressor function

Abstract

Transcriptional regulators play a crucial role in the adaptation of microorganisms to diverse environmental challenges. Most microbial transcriptional regulators contain an effector binding regulatory domain and a DNA-binding domain that interacts with a specific operator DNA to either prevent (transcriptional repressors) or stimulate (transcriptional activators) transcription of a nearby gene(s). Prokaryotic transcriptional regulators have been classified into a number of families based on amino acid sequence similarity and domain architecture. The tetracycline repressor (TetR) family of proteins exhibits a high degree of sequence similarity at the N-terminal DNA-binding domain (∼50 amino acids), which adopts a helix-turn-helix (HTH) motif. In contrast, the regulatory domain is more variable, possibly reflecting the need to specifically accommodate different effectors. TM1030 from Thermotoga maritima, a hyperthermophilic bacterium that typically thrives in high temperature ecosystems, is a 200 amino acid protein with a molecular weight of 24 kDa and an isoelectric point of 6.25. The N-terminal DNA-binding domain of TM1030 shows sequence similarity to members of the TetR family, but no significant similarity is found for the regulatory C-terminal region (∼150 amino acids). Here, we present the crystal structure of a ligand-bound form of TM1030, which was determined to 2.3 A resolution, using the semiautomated, high-throughput pipeline of the Joint Center for Structural Genomics (JCSG) as part of the National Institute of General Medical Sciences (NIGMS)- funded Protein Structure Initiative (PSI).