Helix-Turn-Helix DNA binding domain of transcription regulators from the MerR superfamily; Helix-turn-helix (HTH) transcription regulator MerR superfamily, N-terminal domain. The MerR family transcription regulators have been shown to mediate responses to stress including exposure to heavy metals, drugs, or oxygen radicals in eubacterial and some archaeal species. They regulate transcription of multidrug/metal ion transporter genes and oxidative stress regulons by reconfiguring the spacer between the -35 and -10 promoter elements. A typical MerR regulator is comprised of two distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their N-terminal domains are homologous and contain a DNA-binding winged HTH motif, while the C-terminal domains are often dissimilar and bind specific coactivator molecules such as metal ions, drugs, and organic substrates.

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gi 640290498  25 PFWKKKCLSVNETAAYTGIGRGKIRELMKR-KDCNFMTTDGYQVYVIIDKFVEFLNSRNEI 84
Cdd:pfam09035  2 PIHKKMSLNTKEAAEYSGIGEKKIDQIAGEnEGADFILEVGSHILFKRKEFEDFIDEALTI 62

Excisionase from transposon Tn916; The phage-encoded excisionase protein Tn916-Xis adopts a winged-helix structure that consists of a three-stranded anti-parallel beta-sheet that packs against a helix-turn-helix (HTH) motif and a third C-terminal alpha-helix. It is encoded for by Tn916, which also codes for the integrase Tn916-Int. The protein interacts with DNA by the insertion of helix alpha-2 into the major groove and the contact of the hairpin that connects strands beta-2 and beta-3 with the adjacent phosphodiester backbone and/or minor groove. Tn916-Xis stimulates phage excision and inhibits viral integration by stabilising distorted DNA structures.

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                 ....*....|....*....|....*....|....*....|....*....|....*....|.
gi 640290498  25 PFWKKKCLSVNETAAYTGIGRGKIRELMKR-KDCNFMTTDGYQVYVIIDKFVEFLNSRNEI 84
Cdd:pfam09035  2 PIHKKMSLNTKEAAEYSGIGEKKIDQIAGEnEGADFILEVGSHILFKRKEFEDFIDEALTI 62

Excisionase from transposon Tn916; The phage-encoded excisionase protein Tn916-Xis adopts a winged-helix structure that consists of a three-stranded anti-parallel beta-sheet that packs against a helix-turn-helix (HTH) motif and a third C-terminal alpha-helix. It is encoded for by Tn916, which also codes for the integrase Tn916-Int. The protein interacts with DNA by the insertion of helix alpha-2 into the major groove and the contact of the hairpin that connects strands beta-2 and beta-3 with the adjacent phosphodiester backbone and/or minor groove. Tn916-Xis stimulates phage excision and inhibits viral integration by stabilising distorted DNA structures.

                         10        20        30        40        50        60
                 ....*....|....*....|....*....|....*....|....*....|....*....|.
gi 640290498  25 PFWKKKCLSVNETAAYTGIGRGKIRELMKR-KDCNFMTTDGYQVYVIIDKFVEFLNSRNEI 84
Cdd:pfam09035  2 PIHKKMSLNTKEAAEYSGIGEKKIDQIAGEnEGADFILEVGSHILFKRKEFEDFIDEALTI 62