Help:Regulatory

Revision as of 23:14, 9 July 2006 by Smelissali (Talk | contribs)

Part icon regulatory.png Browse Regulatory parts!

Regulatory parts (also known as 'promoters') are those which provide binding regions for RNA polymerase, the enzyme which performs the act of transcription (the conversion of DNA to RNA).
E.coli's RNA polymerase is a large enzyme which spans about 6 turns of a DNA helix, which is equivalent to about 60 base pairs. Thus many promoter regions for e.coli are approximately 60 bp in length.

Some sub-categories of Regulatory parts are:

Switching Behaviour

This describes whether the default state of the regulatory region is normally in the 'on' (repressible) or 'off' (inducible) state of transcription. More details on each of those two categories below.

Repressible

Regulatory regions which allow for continual transcription of parts. Often these parts can be down-regulated (transcription downregulated) by the addition of ligand. The use of constituitive promoters can be desirable since they are less susceptible to cross-talk and can hypothetically take in PoPS input.

Examples of repressible parts include

  • Part:BBa_R0040 - the pTet promoter region, controlled by tetracycline or its chemical analog [http://openwetware.org/wiki/ATc ATC]
  • Part:BBa_R0011 - the pLac promoter region, controlled by the lactose protein or by its chemical analog [http://openwetware.org/wiki/IPTG IPTG]

Inducible parts

Parts which are continually "off" (transcription is not induced), but allow for activation (increase transcription) through the addition of particular chemicals

Examples include:

  • Part:BBa_R0080 - The araC promoter region, which can be activated by the addition of the sugar [http://openwetware.org/wiki/Arabinose arabinose]
  • Part:BBa_I0500 - Another [http://openwetware.org/wiki/Arabinose arabinose] inducible promoter region


Direction

A regulatory region can point RNA polymerase in either the forward or reverse directions depending on which strand of the double stranded DNA molecule it decides to bind to. Currently most Biobrick regulatory parts transcribe DNA in the forward direction.

References

  1. Ptashne, Mark. "A Genetic Switch". Cold Spring Harbor Press, 1986.