HTH_ASNC

helix_turn_helix ASNC type

• SMART accession number: SM00344
• Description: AsnC: an autogenously regulated activator of asparagine synthetase A transcription in Escherichia coli)
• Interpro abstract (IPR019888):

  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 [ (PUBMED: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 [ (PUBMED:12675791) ].

  Members of the Lrp family are small DNA-binding proteins with molecular masses of around 15kDa. 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 [ (PUBMED:12675791) ].

  This entry also includes some siroheme decarboxylases, which contain the AsnC-like ligand binding domain.

There are 72894 HTH_ASNC domains in 70987 proteins in SMART's nrdb database.

Literature (relevant references for this domain)

Primary literature is listed below; Automatically-derived, secondary literature is also avaliable.

• Kyrpides NC, Ouzounis CA
• The eubacterial transcriptional activator Lrp is present in the archaeon Pyrococcus furiosus.
• Trends Biochem Sci. 1995; 20: 140-1

• Willins DA, Ryan CW, Platko JV, Calvo JM
• Characterization of Lrp, and Escherichia coli regulatory protein that mediates a global response to leucine.
• J Biol Chem. 1991; 266: 10768-74

Exogenous leucine affects the expression of a number of different operons in Escherichia coli. For at least some of these operons, the leucine-related effect is mediated by a protein called Lrp (Leucine-responsive regulatory protein). The purification of Lrp to near homogeneity is described. Lrp is a moderately abundant, basic protein composed of two subunits of molecular mass 18.8 kDa each. In addition, the corresponding protein was purified from a strain having a mutation within the gene that encodes Lrp (lrp). This mutation (lrp-1) causes high constitutive expression of ilvIH, one of the operons controlled by Lrp (Platko, J. V., Willins, D.A., and Calvo, J.M. (1990) J. Bacteriol. 172, 4563-4570). The Lrp-1 and Lrp proteins have similar physical properties, but they show some differences in the characteristics with which they bind DNA upstream of the ilvIH promoter. The nucleotide sequences of the lrp and lrp-1 genes differ by only a single nucleotide, a C to G change that would substitute a Glu for an Asp at amino acid 114. Lrp has some amino acid sequence similarity to AsnC, a protein that regulates asnA expression (Kolling, R., and Lother, H. (1985) J. Bacteriol. 164, 310-315).

Structure (3D structures containing this domain)

3D Structures of HTH_ASNC domains in PDB

PDB code	Title
1i1g	CRYSTAL STRUCTURE OF THE LRP-LIKE TRANSCRIPTIONAL REGULATOR FROM THE ARCHAEON PYROCOCCUS FURIOSUS
1ri7	crystal structure of a protein in the LRP/ASNC family from the hyperthermophilic archaeon Pyrococcus sp. OT3
2cfx	Structure of B.subtilis LrpC
2cg4	Structure of E.coli AsnC
2cyy	Crystal structure of PH1519 from Pyrococcus horikosii OT3
2dbb	Crystal structure of PH0061
2e1c	Structure of Putative HTH-type transcriptional regulator PH1519/DNA Complex
2e7w	Crystal structure of the Lrp/AsnC like transcriptional regulators from Sulfolobus tokodaii 7
2e7x	Structure of the Lrp/AsnC like transcriptional regulator from Sulfolobus tokodaii 7 complexed with its cognate ligand
2efn	Crystal Structure of Ser 32 to Ala of ST1022 from Sulfolobus tokodaii 7
2efo	Crystal structure of Tyr77 to Ala of ST1022 from Sulfolobus tokodaii 7
2efp	Crystal Structure of Tyr77 to Ala of ST1022-Glutamine Complex from Sulolobus tokodaii 7
2efq	Crystal Structure of Thr134 to Ala of ST1022-Glutamine Complex from Sulfolobus tokodaii 7
2gqq	Crystal Structure of E. coli Leucine-responsive regulatory protein (Lrp)
2ia0	Transcriptional Regulatory Protein PF0864 From Pyrococcus Furiosus a Member of the ASNC Family (PF0864)
2ivm	Crystal structure of a transcriptional regulator
2l4a	NMR structure of the DNA-binding domain of E.coli Lrp
2p5v	Crystal Structure of Transcriptional Regulator NMB0573 from Neisseria Meningitidis
2p6s	Crystal Structure of Transcriptional Regulator NMB0573/L-Met Complex from Neisseria Meningitidis
2p6t	CRYSTAL STRUCTURE OF TRANSCRIPTIONAL REGULATOR NMB0573 and L-LEUCINE COMPLEX FROM NEISSERIA MENINGITIDIS
2pmh	Crystal structure of Thr132Ala of ST1022 from Sulfolobus tokodaii
2pn6	Crystal Structure of S32A of ST1022-Gln complex from Sulfolobus tokodaii
2qz8	Crystal structure of Mycobacterium tuberculosis Leucine response regulatory protein (LrpA)
2vbw	Feast or famine regulatory protein (Rv3291c)from M. tuberculosis complexed with L-Phenylalanine
2vbx	Feast or famine regulatory protein (Rv3291c)from M. tuberculosis complexed with L-Phenylalanine
2vby	Feast or famine regulatory protein (Rv3291c)from M. tuberculosis complexed with L-Tyrosine
2vbz	Feast or famine regulatory protein (Rv3291c)from M. tuberculosis complexed with L-Tryptophan
2vc0	Feast or famine regulatory protein (Rv3291c)from M. tuberculosis complexed with L-Leucine
2vc1	Feast or famine regulatory protein (Rv3291c)from M. tuberculosis complexed with L-Methionine
2w24	M. tuberculosis Rv3291c complexed to Lysine
2w25	Crystal structure of Glu104Ala mutant
2w29	Gly102Thr mutant of Rv3291c
2yx4	Crystal Structure of T134A of ST1022 from Sulfolobus tokodaii
2yx7	Crystals structure of T132A mutant of St1022 from sulfolobus tokodaii 7
2zny	Crystal structure of the FFRP
2znz	Crystal structure of FFRP
3i4p	Crystal structure of AsnC family transcriptional regulator from Agrobacterium tumefaciens
4pcq	4PCQ

Links (links to other resources describing this domain)

• INTERPRO: IPR019888
• PFAM: ASNC_trans_reg
• PROSITE: HTH_ASNC_FAMILY