Transcription regulator AsnC/Lrp, ligand binding domain (IPR019887)

Short name: Tscrpt_reg_AsnC/Lrp_C

Domain relationships



The many bacterial transcription regulation proteins which bind DNA through a 'helix-turn-helix' motif can be classified into subfamilies on the basis of sequence similarities. One such family is the AsnC/Lrp subfamily [PMID: 7770911]. The Lrp family of transcriptional regulators appears to be widely distributed among bacteria and archaea, as an important regulatory system of the amino acid metabolism and related processes [PMID: 12675791].

Members of the Lrp family are small DNA-binding proteins with molecular masses of around 15 kDa. Target promoters often contain a number of binding sites that typically lack obvious inverted repeat elements, and to which binding is usually co-operative. LrpA from Pyrococcus furiosus is the first Lrp-like protein to date of which a three-dimensional structure has been solved. In the crystal structure LrpA forms an octamer consisting of four dimers. The structure revealed that the N-terminal part of the protein consists of a helix-turn-helix (HTH) domain, a fold generally involved in DNA binding. The C terminus of Lrp-like proteins has a beta-fold, where the two alpha-helices are located at one side of the four-stranded antiparallel beta-sheet. LrpA forms a homodimer mainly through interactions between the beta-strands of this C-terminal domain, and an octamer through further interactions between the second alpha-helix and fourth beta-strand of the motif. Hence, the C-terminal domain of Lrp-like proteins appears to be involved in ligand-response and activation [PMID: 12675791].

This entry represents the C-terminal regulatory ligand binding domain of the transcription regulator AsnC/Lrp. Structurally this domain has a dimeric alpha/beta barrel fold [PMID: 7770911, PMID: 17374605].

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.