TA Pair: RHH-Fic
#OrganismToxinAntitoxinLocus IDReplicon
1Corynebacterium diphtheriae NCTC 131291672 DIP0007DIP0008NC_002935
2Corynebacterium efficiens YS-314667 CE0013CE0014NC_004369
3Corynebacterium glutamicum ATCC 13032557 NCgl0010NCgl0011NC_003450
4Corynebacterium glutamicum R3693 cgR_0011cgR_0012NC_009342
5Frankia sp. CcI32377 Francci3_1091Francci3_1090NC_007777
6Frankia sp. EAN1pec4612 Franean1_5367Franean1_5368NC_009921
7Frankia sp. EAN1pec4616 Franean1_6451Franean1_6452NC_009921
8Haemophilus somnus 129PT2858 HS_0441HS_0440NC_008309
9Kineococcus radiotolerans SRS30216 = ATCC BAA-1494314 Krad_2677Krad_2676NC_009664
10Methylobacterium radiotolerans JCM 28315238 Mrad2831_6305Mrad2831_6306NC_010509
11Microcystis aeruginosa NIES-8434953 MAE_11960MAE_11970NC_010296
12Nostoc sp. PCC 7120 (Anabaena sp. PCC7120)1767 alr9029asr9028NC_003270
13Rhodococcus jostii RHA12839 RHA1_ro05890RHA1_ro05889NC_008268
14Roseiflexus castenholzii DSM 139414451 Rcas_2210Rcas_2211NC_009767
15Saccharopolyspora erythraea NRRL 23383632 SACE_6555SACE_6556NC_009142
16Streptomyces avermitilis MA-4680 = NBRC 14893434 SAV_7087SAV_7086NC_003155
17Streptomyces coelicolor A3(2)575 SCO5909SCO5908NC_003888
18Streptomyces coelicolor A3(2)560 SCO1248SCO1249NC_003888
19Streptomyces griseus subsp. griseus NBRC 13350 (Streptomyces)5383 SGR_6278SGR_6277NC_010572
20Xanthobacter autotrophicus Py24423 Xaut_0591Xaut_0590NC_009720

Antitoxin domain: RHH. RHH_2: Uncharacterized protein family (UPF0156). This family of proteins are about 80 amino acids in length and their function is unknown. The proteins contain a conserved GRY motif. This family appears to be related to ribbon-helix-helix DNA-binding proteins

Toxin domain: Fic. Fic/Doc family. This family consists of the Fic (filamentation induced by cAMP) protein and doc (death on curing). The Fic protein is involved in cell division and is suggested to be involved in the synthesis of PAB or folate, indicating that the Fic protein and cAMP are involved in a regulatory mechanism of cell division via folate metabolism. This family contains a central conserved motif HPFXXGNG in most members. The exact molecular function of these proteins is uncertain. P1 lysogens of Escherichia coli carry the prophage as a stable low copy number plasmid. The frequency with which viable cells cured of prophage are produced is about 10(-5) per cell per generation. A significant part of this remarkable stability can be attributed to a plasmid-encoded mechanism that causes death of cells that have lost P1. In other words, the lysogenic cells appear to be addicted to the presence of the prophage. The plasmid withdrawal response depends on a gene named doc (death on curing) that is represented by this family. Doc induces a reversible growth arrest of E. coli cells by targetting the protein synthesis machinery. Doc hosts the C-terminal domain of its antitoxin partner Phd (prevents host death) through fold complementation, a domain that is intrinsically disordered in solution but that folds into an alpha-helix on binding to Doc.

(1) Makarova KS et al. (2009) Comprehensive comparative-genomic analysis of type 2 toxin-antitoxin systems and related mobile stress response systems in prokaryotes. Biol Direct 4:19. [PudMed:19493340] in_silico