Policy Issues

Positive control Systems


The inducer–repressor control of the lac operon is an example of negative control, in which expression is normally blocked. In contrast, the CAP-cAMP system is an example of positive control, because expression of the lac operon requires the presence of an activating signal—in this case, the interaction of the CAP-cAMP complex with the CAP region. distinguishes between these two basic types of control systems.

Comparison of positive and negative control. The basic aspects of negative and positive control are depicted. (a) In negative control, an active repressor (encoded by the gene in the example shown here) blocks gene expression of the A B C (more...)

For activators or repressor proteins to do their job, each must be able to exist in two states: one that can bind its DNA targets and one that cannot. The binding state must be appropriate for a given set of environmental conditions. For many activator or repressor proteins, the way that DNA binding is regulated is through the interaction of two different sites in the three-dimensional structure of the protein. One site is the DNA-binding domain. The other site, the allosteric site, acts as a switch that sets the DNA-binding domain in one of two modes: functional or nonfunctional. The allosteric site interacts with small molecules called allosteric effectors. In regard to the lac operon, the lac inducers are allosteric effectors. When allosteric effectors bind to the allosteric site, they cause a conformational change in the regulatory protein so that it alters the structure of the DNA-binding domain. Some activator or repressor proteins must bind to their allosteric effectors to bind DNA. Others can bind DNA only in the absence of their allosteric effectors. depicts these concepts.

The effects of allosteric effectors on the DNA-binding activities of activators and repressors.

By agreement with the publisher, this book is accessible by the search feature, but cannot be browsed.



Share this article





Related Posts


Traction control systems
Traction control systems
Attitude control Systems
Attitude control Systems
SunTouch control Systems
SunTouch control Systems

Latest Posts
Open loop Meaning
Open loop Meaning
In the continuing quest to find meaning…
Traction control system warning Light
Traction control…
Traction control systems are very common…
Motorcycle Traction control system
Motorcycle Traction…
Traction Control is the latest must-have…
Aircraft Flight Control Systems
Aircraft Flight…
Aircraft manufacturers are consolidating…
Open loop diagram
Open loop diagram
[sysp, sysc] = getlinplant(block, op)…
Search
Featured posts
  • Traction control systems
  • Attitude control Systems
  • SunTouch control Systems
  • Industrial Wireless Control Systems
  • Flight Control Systems
  • Security Access Control Systems
  • Stage lighting control systems
  • Best home lighting control systems
  • Microlite lighting control systems
Copyright © 2017 l www.oliver-control.com. All rights reserved.