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33 Cards in this Set

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  • Back
What are the three types of regulation of a pre-exisiting enzyme (posttranslational)
1. Inhibit enzyme activity
2. Modification of the enzyme
3. Turn over or degradation
What are three ways to regulate amount of enzyme synthesized?
1. Transcription regulation
2. Regulation of mRNA stability
3. Regluation on translation
Feedback inhibition
The end product of the pathway affects the activity of the first enzyme in the pathway.
Allosteric enzyme
Enzyme has two binding sitesm one for substrate and a second site that binds the allosteric regulator.
Conformational Change
Renders the enzyme inactive when regulator is bound.
Example of feedback inhibition?
proline and arginine biosynthesis; both include glutamic acid
What does Arginine inhibit?
N-acetyl glutamate synthesis (AGS)
What does Proline inhibit?
glutamyl kinase (GK)
Multiple enzymes that carryout the same reaction, and are independently regulated.
What is an example of a izoenymatic pathway?
DAHP synthesis
What is an example of a covalently modified pathway?
Glutamine sythetase
Where does reglaution of transcription frequently occur?
In the initiation step.
What does reglulation usually involve?
A sequence specific interaction of a regulatory protein with DNA, RNA polymerase or both.
Regulators that stimulate transcription
Regulators that inhibit transcription.
Inverted Repeats
The target of DNA
What are proteins that interact with IR's often like?
Dimers, with each polypeptide haveing a domain that interacts within the major grove.
Has two helices seperated by a short turn sequence. The recognition helix interacts with the DNA and the stablizing helix plays a structural role. They are often dimers.
What type of organisms do HTH normally regulate?
Sn-Finger proteins
This domain binds a Zn2+ ion. Zn is usu bound by Cys and His (4 ligands) and the helical region has the DNA binding elements.
What type of organisms fo Zn-Finger proteins commonly interact with?
Leucine Zipper
A repeating pattern of leucine on the outer-face of the helix facilitates an interaction between two proteins. The DNA binding domain is usu a separate helical region on the protein.
What is an example of a HTH?
Lambda Cro
Enzyme synthesis does not occur when the enzymes' product is present in the medium.
Enzyme synthesis occurs only when its substrate is present in the medium
Example of repression?
common in AA, Purines, and pyrimidines
Example of Induction?
common in catabolic pathways for carbon and energy sources
What is an example of an allosteric regulator?
ArgR only binds DNA when corepressor (arginine) is bound.
What is an example of an enzyme that binds to the DNA blocking transcription when the repressor is absent?
Positive control
Regulator proteins promote the binding of RNA polymerase, which leads to an increase in transcription.
What is an example of an allosteric protein that binds DNA in the presence of an inducer?
How do activator proteins activate transcription?
By aiding in the binding of RNAP to the promoter or helping the complex begin the transcription process.
A single regulator protein controls the expression of multiple operons.