Protein Domain : Transcription regulator AsnC-like IPR019888

Type	Family
Description	The many bacterial transcription regulation proteins which bind DNA through a 'helix-turn-helix' motif can be classified into subfamilies on the basis ofsequence similarities. One such family is the AsnC/Lrp subfamily [ ]. The Lrp family of transcriptional regulators appears to be widely distributed among bacteria andarchaea, as an important regulatory system of the amino acid metabolism and related processes [ ]. Members of the Lrp family are small DNA-binding proteins with molecular masses of around 15kDa. Target promoters often contain anumber 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 structurehas 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 ahelix-turn-helix (HTH) domain, a fold generally involved in DNA binding. The C terminus of Lrp-like proteins has a β-fold, where the two α-helices are located at one side of the four-stranded antiparallel β-sheet.LrpA forms a homodimer mainly through interactions between the β-strands of this C-terminal domain, and an octamer through further interactions between the second α-helix and fourth β-strandof the motif. Hence, the C-terminal domain of Lrp-like proteins appears to be involved in ligand-response and activation [].This entry also includes some siroheme decarboxylases, which contain the AsnC-like ligand binding domain.
Short Name	Tscrpt_reg_AsnC-like