Glycine riboswitch explained

Glycine
Symbol:Glycine
Rfam:RF00504
Rna Type:Cis-reg
Riboswitch

The bacterial glycine riboswitch is an RNA element that can bind the amino acid glycine. Glycine riboswitches usually consist of two metabolite-binding aptamer domains with similar structures in tandem. The aptamers were originally thought to cooperatively bind glycine to regulate the expression of downstream genes. In Bacillus subtilis, this riboswitch is found upstream of the gcvT operon which controls glycine degradation. It is thought that when glycine is in excess it will bind to both aptamers to activate these genes and facilitate glycine degradation.[1]

The originally discovered, truncated version of the glycine riboswitch exhibits sigmoidal binding curves with Hill coefficients greater than one, which led to the idea of positive cooperativity between the two aptamer domains.[1] [2] Data in 2012 shows that cooperative binding does not occur in the switch with its extended 5' leader, though the purpose of the switch's dual aptamers is still uncertain.[3]

Atomic resolution structures of portions of glycine riboswitches have been obtained by X-ray crystallography.[4] [5]

In vivo experiments demonstrated that glycine does not need to bind both aptamers for regulation. Mutation to the first aptamer caused greatest reduction in downstream gene expression, while mutation to the second one had varying effects. Glycine-induced expression of the gcvT operon is needed for B. subtilise growth, swarming motility and biofilm formation (in high glycine environment).[6]

See also

Notes and References

  1. Mandal M, Lee M, Barrick JE, Weinberg Z, Emilsson GM, Ruzzo WL, Breaker RR . A glycine-dependent riboswitch that uses cooperative binding to control gene expression . Science . 306 . 5694 . 275–279 . October 2004 . 15472076 . 10.1126/science.1100829 . 2004Sci...306..275M . 14311773 .
  2. Kwon M, Strobel SA . Chemical basis of glycine riboswitch cooperativity . RNA . 14 . 1 . 25–34 . January 2008 . 18042658 . 2151043 . 10.1261/rna.771608 .
  3. Sherman EM, Esquiaqui J, Elsayed G, Ye JD . An energetically beneficial leader-linker interaction abolishes ligand-binding cooperativity in glycine riboswitches . RNA . 18 . 3 . 496–507 . March 2012 . 22279151 . 3285937 . 10.1261/rna.031286.111 .
  4. Butler EB, Xiong Y, Wang J, Strobel SA . Structural basis of cooperative ligand binding by the glycine riboswitch . Chemistry & Biology . 18 . 3 . 293–298 . March 2011 . 21439473 . 10.1016/j.chembiol.2011.01.013 . 3076126 .
  5. Huang L, Serganov A, Patel DJ . Structural insights into ligand recognition by a sensing domain of the cooperative glycine riboswitch . Molecular Cell . 40 . 5 . 774–786 . December 2010 . 21145485 . 3726718 . 10.1016/j.molcel.2010.11.026 .
  6. Babina AM, Lea NE, Meyer MM . Bacillus subtilis . mBio . 8 . 5 . October 2017 . 29089431 . 5666159 . 10.1128/mBio.01602-17 .