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. 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.

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]