| cd10153 | RcnR-FrmR-like_DUF156 | 0.007 | 31 | 52 | 22 | +
Transcriptional regulators RcnR and FrmR, and related domains; this domain family was previously known as part of DUF156. This domain family includes various transcriptional regulators that respond to different stressors. It includes Escherichia coli RncR (formally known as YohL, nickel and cobalt-sensitive), and E. coli FrmR (formally known as YaiN, formaldehyde sensitive). Escherichia coli RncR represses expression of the gene encoding the nickel and cobalt-efflux protein RcnA; RcnA may act through modulating NikR, to repress the NIkABCDE nickel transporter. In vitro, purified RncR binds to the rncA promoter DNA fragment in the absence of Ni2+ or Co2+, and the affinity of RncR for this promoter is reduced in the presence of excess nickel. Escherichia coli FrmR regulates the formaldehyde degradation frmRAB operon. This family belongs to a larger superfamily that includes CsoRs (copper-sensitive operon repressors). CsoRs form homotetramers (dimer of dimers). In Mycobacterium tuberculosis CsoR, within each dimer, two Cys residues on opposite subunits, along with a His residue, bind the Cu(I) ion (forming a triagonal S2N coordination complex, C-H-C). These residues are conserved in the majority of members of this superfamily. In this family, however, not all these residues are conserved; in E.coli RcnR and FrmR there is a His or a Thr instead of the second Cys (C-H-H or C-H-T) respectively. For E. coli FrmR, an N-terminal His residue, not conserved in all members of this family, is also involved in metal binding (H-C-H-H). A conserved Tyr and a Glu residue that facilitate allosteric regulation of DNA binding for CsoRs are poorly conserved in this family. |
| smart00768 | X8 | 6.0e-32 | 20 | 106 | 87 | +
Possibly involved in carbohydrate binding. The X8 domain, which may be involved in carbohydrate binding, is found in an Olive pollen antigen as well as at the C terminus of family 17 glycosyl hydrolases. It contains 6 conserved cysteine residues which presumably form three disulfide bridges. |
