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