Part:BBa_K4604031

K12 AdoCbl riboswitch

This Biobrick is a riboswitch for AdoCbl, a bioavailable form of B12. Upon binding to AdoCbl, a conformational change happens within the riboswitch, negatively regulating the gene downstream of it. It includes a Shine-Dalgarno sequence. To verify the performance of the riboswitch we created several sensors with a fluorescent readout: BBa_K4604026, BBa_K4604027, BBa_K4604028 and BBa_K4604029.

Usage and Biology

Riboswitches occur naturally as regulators of gene expression. Riboswitches are encoded as DNA sequences which exert their regulatory effect upon transcription by folding into a complex 3D structure. Generally, a riboswitch can fold in such a way that the ribosome binding site (RBS) is available or unavailable for the ribosome. Upon binding to the target compound, like AdoCbl, a configurational change in the riboswitch changes the availability of the RBS. In E. coli a riboswitch regulates the expression of the btuB gene which encodes for a corrine transporter protein BtuB. It has been shown that when sufficient AdoCbl is present, the riboswitch undergoes a conformational change resulting in lower BtuB expression.

Figure 1: Riboswitch regulatory mechanism. (A) Binding of compounds leads to a conformational change and the formation of a terminator stem (UUU), which leads to termination of transcription. (B) Translational regulation: The conformational change of the riboswitch covers the ribosome binding site (RBS), preventing the ribosome from binding to the mRNA, thereby hindering translation. Made with biorender.com

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  COMPATIBLE WITH RFC[21]
• 23
  COMPATIBLE WITH RFC[23]
• 25
  INCOMPATIBLE WITH RFC[25]

  Illegal NgoMIV site found at 162
  
• 1000
  COMPATIBLE WITH RFC[1000]