FlmA-FlmB toxin-antitoxin system explained

flmB
Symbol:	FlmB
Tax Domain:	E. coli, S. enterica

The FlmA-FlmB toxin-antitoxin system consists of FlmB RNA (F leading-region maintenance B), a family of non-coding RNAs and the protein toxin FlmA. The FlmB RNA transcript is 100 nucleotides in length and is homologous to sok RNA from the hok/sok system and fulfills the identical function as a post-segregational killing (PSK) mechanism.^{[1] [2]}

flmB is found on the F-plasmid of Escherichia coli and Salmonella enterica. It is responsible for stabilising the plasmid. If the plasmid is not inherited, long-lived FlmA mRNA and protein will be highly toxic to the cell, possibly to the point of causing cell death. Daughter cells which inherit the plasmid inherit the FlmB gene, coding for FlmB RNA which binds the leader sequence of FlmA mRNA and represses its translation.

See also

• Toxin-antitoxin system
• IstR RNA
• RdlD RNA
• Sib RNA
• SymR RNA
• ptaRNA1

Further reading

• Fozo EM, Makarova KS, Shabalina SA, Yutin N, Koonin EV, Storz G . Abundance of type I toxin–antitoxin systems in bacteria: searches for new candidates and discovery of novel families . Nucleic Acids Res. . 38 . 11 . 3743–3759 . June 2010 . 20156992 . 2887945 . 10.1093/nar/gkq054 .
• Fozo EM, Hemm MR, Storz G . Small Toxic Proteins and the Antisense RNAs That Repress Them . Microbiol. Mol. Biol. Rev. . 72 . 4 . 579–589, Table of Contents . December 2008 . 19052321 . 2593563 . 10.1128/MMBR.00025-08 .
• Gerdes K, Wagner EG . RNA antitoxins . Curr. Opin. Microbiol. . 10 . 2 . 117–124 . April 2007 . 17376733 . 10.1016/j.mib.2007.03.003 .
• Hayes F . Toxins-antitoxins: plasmid maintenance, programmed cell death, and cell cycle arrest . Science . 301 . 5639 . 1496–1499 . September 2003 . 12970556 . 10.1126/science.1088157 . 10028255 .

Notes and References

1. Loh SM, Cram DS, Skurray RA . Nucleotide sequence and transcriptional analysis of a third function (Flm) involved in F-plasmid maintenance . Gene . 66 . 2 . 259–268 . June 1988 . 3049248 . 10.1016/0378-1119(88)90362-9.
2. Kobayashi M, Kurusu Y, Yukawa H . High-expression of a target gene and high-stability of the plasmid . Appl. Biochem. Biotechnol. . 27 . 2 . 145–162 . February 1991 . 2029184 . 10.1007/BF02921523. 41601297 .