InterPro domain: IPR012318

The Crp-type HTH domain is a DNA-binding, winged helix-turn-helix (wHTH)domain of about 70-75 amino acids present in transcription regulators of thecrp-fnr family, involved in the control of virulence factors, enzymes ofaromatic ring degradation, nitrogen fixation, photosynthesis, and varioustypes of respiration. The Crp-Fnr family is named after the first membersidentified in Escherichia coli: the well characterised cyclic AMP receptor protein CRPor CAP (catabolite activator protein) and the fumarate and nitrate reductaseregulator Fnr. Crp-type HTH domain proteins occur in most bacteria and inchloroplasts of red algae. The DNA-binding HTH domain is located in theC-terminal part; the N-terminal part of the proteins of the Crp-Fnr familycontains a nucleotide-binding domain and adimerization/linker helix occurs in between. The Crp-Fnr regulatorspredominantly act as transcription activators, but can also be importantrepressors, and respond to diverse intracellular and exogenous signals, suchas cAMP, anoxia, redox state, oxidative and nitrosative stress, carbonmonoxide, nitric oxide or temperature [ 1 , 2 ].

1. Lactobacillus casei contains a member of the CRP-FNR family. Nucleic Acids Res. 21, 753
2. Phylogeny of the bacterial superfamily of Crp-Fnr transcription regulators: exploiting the metabolic spectrum by controlling alternative gene programs. FEMS Microbiol. Rev. 27, 559-92