This is the RNA polymerase interacting domain (RID) of transcription-repair-coupling factor (TRCF), CarD and CarD homologue in Myxococcus xanthus, called CdnL. In Myxococcus xanthus, CdnL is a protein required for the activation of light- and starvation-inducible genes [1]. It interacts with the zinc-binding protein CarG to form a complex that regulates multiple processes in Myxococcus xanthus [4]. CarD is widely distributed among bacteria and represents a distinct class of RNAP binding proteins that regulate transcription and essential processes [4-8]. TRCF displaces RNA polymerase stalled at a lesion, binds to the damage recognition protein UvrA, and increases the template strand repair rate during transcription [3].

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2: Domain architecture of a high mobility group A-type bacterial transcriptional factor. Padmanabhan S, Elias-Arnanz M, Carpio E, Aparicio P, Murillo FJ; J Biol Chem 2001;276:41566-41575. PMID:11533063

3: Structure and function of transcription-repair coupling factor. I. Structural domains and binding properties. Selby CP, Sancar A; J Biol Chem 1995;270:4882-4889. PMID:7876261

4: Recruitment of a novel zinc-bound transcriptional factor by a bacterial HMGA-type protein is required for regulating multiple processes in Myxococcus xanthus. Penalver-Mellado M, Garcia-Heras F, Padmanabhan S, Garcia-Moreno D, Murillo FJ, Elias-Arnanz M; Mol Microbiol. 2006;61:910-926. PMID:16879646

5: CdnL, a member of the large CarD-like family of bacterial proteins, is vital for Myxococcus xanthus and differs functionally from the global transcriptional regulator CarD. Garcia-Moreno D, Abellon-Ruiz J, Garcia-Heras F, Murillo FJ, Padmanabhan S, Elias-Arnanz M; Nucleic Acids Res. 2010;38:4586-4598. PMID:20371514

6: Structural basis for bacterial transcription-coupled DNA repair. Deaconescu AM, Chambers AL, Smith AJ, Nickels BE, Hochschild A, Savery NJ, Darst SA; Cell. 2006;124:507-520. PMID:16469698

7: Crystal structure of Mycobacterium tuberculosis CarD, an essential RNA polymerase binding protein, reveals a quasidomain-swapped dimeric structural architecture. Kaur G, Dutta D, Thakur KG; Proteins. 2014;82:879-884. PMID:24115125

8: Structure and function of CarD, an essential mycobacterial transcription factor. Srivastava DB, Leon K, Osmundson J, Garner AL, Weiss LA, Westblade LF, Glickman MS, Landick R, Darst SA, Stallings CL, Campbell EA; Proc Natl Acad Sci U S A. 2013;110:12619-12624. PMID:23858468