World Library  
Flag as Inappropriate
Email this Article

Inducer

Article Id: WHEBN0003631372
Reproduction Date:

Title: Inducer  
Author: World Heritage Encyclopedia
Language: English
Subject: Operon, Expression vector, SCCmec, Enzyme inducer, Regulator gene
Collection: Gene Expression, Organic Compounds
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Inducer

In molecular biology, an inducer is a molecule that regulates gene expression.[1] An inducer can bind to repressors or activators.

Inducers function by disabling repressors. The gene is expressed because an inducer binds to the repressor. The binding of the inducer to the repressor prevents the repressor from binding to the operator. RNA polymerase can then begin to transcribe operon genes.

Inducers also function by binding to activators. Activators generally bind poorly to activator DNA sequences unless an inducer is present. Activator binds to an inducer and the complex binds to the activation sequence and activates target gene.[2] Removing the inducer stops transcription.[2]

Because a small inducer molecule is required, the increased expression of the target gene is called induction.[2] The lactose operon is one example of an inducible system.[2]

Contents

  • Function 1
  • Examples 2
    • lac operon 2.1
    • ara operon 2.2
  • References 3
  • External links 4

Function

Repressor proteins bind to the DNA strand and prevent RNA polymerase from being able to attach to the DNA and synthesize mRNA. Inducers bind to repressors, causing them to change shape and preventing them from binding to DNA. Therefore, they allow transcription, and thus gene expression, to take place.

For a gene to be expressed, its DNA sequence must be copied (in a process known as transcription) to make a smaller, mobile molecule called messenger RNA (mRNA), which carries the instructions for making a protein to the site where the protein is manufactured (in a process known as translation). Many different types of proteins can affect the level of gene expression by promoting or preventing transcription. In prokaryotes (such as bacteria), these proteins often act on a portion of DNA known as the operator at the beginning of the gene. The promoter is where RNA polymerase, the enzyme that copies the genetic sequence and synthesizes the mRNA, attaches to the DNA strand.

Some inducers are modulated by activators, which have the opposite effect on gene expression as repressors. Inducers bind to activator proteins, allowing them to bind to the DNA strand where they promote RNA transcription.

Ligands that bind to deactivate activator proteins are not, in the technical sense, classified as inducers, since they have the effect of preventing transcription.

Examples

lac operon

The inducer in the lac operon is allolactose.[2] If lactose is present in the medium, then a small amount of it will be converted to allolactose by a few molecules of β-galactosidase that are present in the cell.[3] Allolactose binds to the repressor and decreases the repressor's affinity for the operator site.[3]

However, when lactose and glucose are both available in the system, the lac operon is repressed. This is because glucose actively prevents the induction of lacZYA.[2]

ara operon

In the ara operon, arabinose is the inducer.

References

  1. ^ Baraniak, P. R.; Nelson, D. M.; Leeson, C. E.; Katakam, A. K.; Friz, J. L.; Cress, D. E.; Hong, Y; Guan, J; Wagner, W. R. (2011). "Spatial control of gene expression within a scaffold by localized inducer release". Biomaterials 32 (11): 3062–71.  
  2. ^ a b c d e f Slonczewski, Joan, and John Watkins. Foster. Microbiology: An Evolving Science. New York: W.W. Norton &, 2009. Print.
  3. ^ a b Biology Part 2. Berkeley, CA: Berkeley Review, 1995. Print.

External links

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 



Copyright © World Library Foundation. All rights reserved. eBooks from Hawaii eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.