1.C.64 The Fst Toxin (Fst) Family

The Fst toxin is a 33 amino acid peptide toxin encoded by a stable RNAI message of the partition (par) toxin-antitoxin stability determinant of the Enterococcus faecalis conjugative plasmid, pAD1 (Weaver et al., 2003). It shows no significant sequence similarity to other proteins in the NCBI database (4/03). Intracellular production of Fst inhibits macromolecular synthesis, inhibits cell growth, and renders the cell permeable to the DNA stain, Sytox Green, which cannot normally pass through the membrane. Fst increased the number of cells stained at least 10-fold, but did not allow nutrient efflux. It may allow selective pore formation. It functions synergistically with nisin, a lantibiotic pore former (see TC #1.C.30.1.1). Mutants resistant to Fst have altered membrane composition (Weaver et al., 2003).


 

References:

Nonin-Lecomte, S., L. Fermon, B. Felden, and M.L. Pinel-Marie. (2021). Bacterial Type I Toxins: Folding and Membrane Interactions. Toxins (Basel) 13:.
Weaver, K.E., D.M. Weaver, C.L. Wells, C.M. Waters, M.E. Gardner, and E.A. Ehli. (2003). Enterococcus faecalis plasmid pAD1-encoded Fst toxin affects membrane permeability and alters cellular responses to lantibiotics. J. Bacteriol. 185: 2169-2177.
Examples:

TC#NameOrganismal TypeExample
1.C.64.1.1

Fst peptide toxin of 33 aas and 1 TMS. It's 3-d structure is known (2KV5) and is identical to the Fst toxin from Enterococcus faecalis (Nonin-Lecomte et al. 2021).

Enterococci

Fst of plasmid pAD1 of Enterococcus faecalis

 
1.C.64.1.10

Putative toxic peptide of 33 aas and 1 TMS

Toxic peptide of Lactococcus lactis

 
1.C.64.1.11

Type I toxin-antitoxin system, Fst family toxin, of 30 aas and 1 TMS.

Toxin of Streptococcus mitis

 
1.C.64.1.12

Toxic peptide of 29 aas and 1 TMS (plasmid-encoded).

toxin of Lacticaseibacillus rhamnosus

 
1.C.64.1.13

Small polypeptide toxin of 35 aas and 1 TMS, LdrD.  Its 3-d structure is known (PDB # 5LBJ) (Nonin-Lecomte et al. 2021).

LdrD of Escherichia coli (strain K12)

 
1.C.64.1.14

Type I toxin-antitoxin system Fst family toxin, PepA1 or SprA1, of 31 aas and 1 TMSs.  It's 3-d structure is known (PDB # 4B19) (Nonin-Lecomte et al. 2021)

PEPA1 of Staphylococcus aureus

 
1.C.64.1.15

Type I toxin-antitoxin system Fst family toxin of 32 aas and 1 TMS.

Toxin of Staphylococcus sp.

 
1.C.64.1.2

Toxic peptide of 31 aas and 1 TMS

Toxic peptide of Enterococcus hirae

 
1.C.64.1.3

Putative toxic peptide of 32 aas and 1 TMS.

Peptide of Streptococcus agalactiae

 

 
1.C.64.1.4

Putative toxic peptide of 32 aas and 1 TMS

Toxic peptide of Streptococcus mutans

 
1.C.64.1.5

Toxic peptide of 35 aas and 1 TMS

Toxic peptide of Lactobacillus gasseri

 
1.C.64.1.7

type I toxin-antitoxin system Fst family toxin of 29 aas and 1 TMS

Toxin of Lactobacillus casei

 
1.C.64.1.8

Type I toxin-antitoxin system, Fst family toxin, of 31 aas and 1 TMS.

Toxin of Staphylococcus epidermidis

 
1.C.64.1.9

Uncharacterized protein of 31 aas and 1 TMS

UP of Streptococcus pyogenes

 
Examples:

TC#NameOrganismal TypeExample