MqsR_toxin is a family of bacterial toxins that act as an mRNA interferase. MqsR is the gene most highly upregulated in E. coli persister cells [2] and it plays an essential role in biofilm regulation [3] and cell signalling [4]. It forms part of a bacterial toxin-antitoxin TA system, and as expected for a TA system, the expression of the MqsR toxin leads to growth arrest, while co-expression with its antitoxin, MqsA, rescues the growth arrest phenotype. In addition, MqsR associates with MqsA to form a tight, non-toxic complex and both MqsA alone and the MqsR:MqsA2:MqsR complex bind and regulate the mqsR promoter. The structure of MqsR shows that is is a member of the RelE/YoeB family of bacterial RNases that are structurally and functionally characterised bacterial toxins.y characterized bacterial toxins [1].

1: Three dimensional structure of the MqsR:MqsA complex: a novel TA pair comprised of a toxin homologous to RelE and an antitoxin with unique properties. Brown BL, Grigoriu S, Kim Y, Arruda JM, Davenport A, Wood TK, Peti W, Page R; PLoS Pathog. 2009;5:e1000706. PMID:20041169

2: Persisters: a distinct physiological state of E. coli. Shah D, Zhang Z, Khodursky A, Kaldalu N, Kurg K, Lewis K; BMC Microbiol. 2006;6:53. PMID:16768798

3: Autoinducer 2 controls biofilm formation in Escherichia coli through a novel motility quorum-sensing regulator (MqsR, B3022). Gonzalez Barrios AF, Zuo R, Hashimoto Y, Yang L, Bentley WE, Wood TK; J Bacteriol. 2006;188:305-316. PMID:16352847

4: Gene expression in Escherichia coli biofilms. Ren D, Bedzyk LA, Thomas SM, Ye RW, Wood TK; Appl Microbiol Biotechnol. 2004;64:515-524. PMID:14727089