ribbon-helix-helix domain of Shewanella oneidensis type II antitoxin CopA(SO), and similar proteins; This family includes the N-terminal ribbon-helix-helix (RHH) domain of Shewanella oneidensis CopA(SO), a newly identified type II antitoxin, as well as the N-terminal RHH domain of Escherichia coli PutA flavoprotein, among other similar proteins, many of which are as yet uncharacterized. CopA(SO) is a typical RHH antitoxin that includes an ordered N-terminal domain (CopA(SO)-N) and a disordered C-terminal domain (CopA(SO)-C). Biophysical investigation indicates allosteric effects of CopA(SO)-N on CopA(SO)-C; DNA binding of CopA(SO)-N appears to induce CopA(SO)-C to fold and self-associate the C-terminal domain. The multifunctional E. coli proline utilization A (PutA) flavoprotein functions as a membrane-associated proline catabolic enzyme as well as a transcriptional repressor of the proline utilization genes putA and putP. The N-terminal domain of PutA is a transcriptional regulator with an RHH fold; structure studies show that it forms a homodimer to bind one DNA duplex. This family also includes orphan antitoxin ParD2, an antitoxin component of a non-functional type II toxin-antitoxin (TA system); it does not neutralize the effect of any of the RelE or ParE toxins.

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gi 1154153417 10 QVVSVQMPADLVDAMDRYGEAIERPRSWVMREAVASYLAYEAEK 53
Cdd:cd22233    1 TTLSVRLDDDLKERLDRLAAATDRSRSWIIKEAIEEYLEREEWR 44

ribbon-helix-helix domain of Shewanella oneidensis type II antitoxin CopA(SO), and similar proteins; This family includes the N-terminal ribbon-helix-helix (RHH) domain of Shewanella oneidensis CopA(SO), a newly identified type II antitoxin, as well as the N-terminal RHH domain of Escherichia coli PutA flavoprotein, among other similar proteins, many of which are as yet uncharacterized. CopA(SO) is a typical RHH antitoxin that includes an ordered N-terminal domain (CopA(SO)-N) and a disordered C-terminal domain (CopA(SO)-C). Biophysical investigation indicates allosteric effects of CopA(SO)-N on CopA(SO)-C; DNA binding of CopA(SO)-N appears to induce CopA(SO)-C to fold and self-associate the C-terminal domain. The multifunctional E. coli proline utilization A (PutA) flavoprotein functions as a membrane-associated proline catabolic enzyme as well as a transcriptional repressor of the proline utilization genes putA and putP. The N-terminal domain of PutA is a transcriptional regulator with an RHH fold; structure studies show that it forms a homodimer to bind one DNA duplex. This family also includes orphan antitoxin ParD2, an antitoxin component of a non-functional type II toxin-antitoxin (TA system); it does not neutralize the effect of any of the RelE or ParE toxins.

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                 ....*....|....*....|....*....|....*....|....
gi 1154153417 10 QVVSVQMPADLVDAMDRYGEAIERPRSWVMREAVASYLAYEAEK 53
Cdd:cd22233    1 TTLSVRLDDDLKERLDRLAAATDRSRSWIIKEAIEEYLEREEWR 44

ribbon-helix-helix domains of transcription repressor CopG, nickel responsive transcription factor NikR, and similar proteins; This family includes the ribbon-helix-helix (RHH) domains of transcriptional repressor CopG, nickel-responsive transcription factor NikR, several antitoxins such as Shewanella oneidensis CopA(SO), Burkholderia pseudomallei HicB, and Caulobacter crescentus ParD, and similar proteins. CopG, a homodimeric RHH protein of around 45 residues, constitutes one of the smallest natural transcriptional repressors characterized and is the prototype of a series of repressor proteins encoded by plasmids that exhibit a similar genetic structure at their leading strand initiation and control regions. It is involved in the control of plasmid copy number. NikR, which consists of the N-terminal DNA-binding RHH domain and the C-terminal metal-binding domain (MBD) with four nickel ions, regulates several genes; in Helicobacter pylori, NikR regulates the urease enzyme under extreme acidic conditions, and is involved in the intracellular physiology of nickel. Protein HicB is part of the HicAB toxin-antitoxin (TA) system, where the toxins are RNases, found in many bacteria. In Burkholderia pseudomallei, the HicAB system may play a role in disease by regulating the frequency of persister cells, while in Yersinia pestis HicB acts as an autoregulatory protein that inhibits HicA, which acts as an mRNase. In Escherichia coli, an excess of HicA has been shown to de-repress a HicB-DNA complex and restore transcription of HicB. The CopG family RHH domain, represented by this model, forms a homodimer and binds DNA.

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gi 1154153417 12 VSVQMPADLVDAMDRYGEAIERPRSWVMREAVASYLA 48
Cdd:cd21631    3 VTIKLDDELLERLDELARKRGVSRSELIREALREYLE 39