vapBC

VapBC (virulence associated proteins B and C) is the largest family of type II toxin-antitoxin system genetic loci in prokaryotes.^[1] VapBC operons consist of two genes: VapC encodes a toxic PilT N-terminus (PIN) domain, and VapB encodes a matching antitoxin.^[2] The toxins in this family are thought to perform RNA cleavage, which is inhibited by the co-expression of the antitoxin, in a manner analogous to a poison and antidote.

First discovered in 1992, vapBC loci are now thought make up around 37–42% of all type II toxin-antitoxin systems.^[3][4]

Discovery

Following the discoveries of two other type II toxin-antitoxin systems,

VapBC operons have been found in distantly related prokaryotes, including the pathogens Leptospira interrogans,^[9] Mycobacterium tuberculosis^[10] and Piscirickettsia salmonis.^[11] The loci have been described as "surprisingly abundant, especially in Archaea"^[12]—vapBC family members made up 37% of all TA families identified by one bioinformatics search^[3] and 42% of those found by another.^[4]

VapC toxins, specifically the PIN domains, act as

VapC is strongly inhibited by direct protein interaction with VapB, its cognate antitoxin. The toxin-antitoxin complex is thought to autoregulate its own operon, repressing transcription of both components through a DNA-binding domain in VapB.[17]

In some organisms, vapBC loci have been assigned other potential functions. In the

• Toxin-antitoxin database

References