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18 Cards in this Set
- Front
- Back
What are the two major modes of regulation in the cell? Which would be the quickest?
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1. Post-translational regulation
-Inhibition -Modification of an enzyme -Turnover or degradation 2. Regulation of the amt of enzyme synthesized -Transcription regulator -Regulation of mRNA stability -Regulation of translation 3. Glutamate synthase is fastest way of regulation. |
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What are the key features of an enzyme that is subject to allosteric regulation
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An allosteric enzyme has two binding sites, one for substrate and a second site that binds the allosteric regulator. When the allosteric regulator is bound the enzyme undergoes a conformational change that renders it inactive.
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Feedback inhibition
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A major mechanism for controlling enzyme activity in biosynthetic pathways, here the end product of the pathway affects the activity of the first enzyme in the pathway.
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How is glutamine synthetase activity regulated by covalent modification?
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-It is regulated in part by covalent modification.
-The activity of Glutamine Synthetase decreases linearly with increasing modification |
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Isozymes
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Multiple enzymes that carryout the same reaction, isozymes, and each isozyme is independantly regulated.
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How does intein removal differ from intron splicing?
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-Intein mediated protein splicing occurs Post-Translationallly
-Intron splicing occurs after transcription and before translation. |
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What stage of transcription is most often effected by regulatory proteins? What types of protein domains are common among these proteins and what types of DNA sequences do they recognize.
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-Transcription is most often interrupted at the initiation step, regulation usually involves the sequence-specific interaction of a regulatory protein with DNA, RNA polymerase or both.
Domains include: -Helix, turn-Helix -Zn-finger -Leucine Zipper |
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Helix, Turn-Helix
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Stabilizes helices of the dimer usually interact with each other to form a dimer and the recognition helices interact with the DNA. This domain is common in bacterial regulators.
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Zn-finger
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This domain binds a Zn ion. Zn is usually bound by Cys and His and the helical region has the DNA binding elements. This type of protein is common in eukaryal cells
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Leucine Zippers
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A repeating pattern of LEU on the outer face of the helix faciliates an interaction between two proteins. The DNA binding domain is usually a separate helical region on the proteins.
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Negative control of transcription
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1. Repression
2. Induction |
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Repression
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Often the enzymes catalyzing the synthesis of a compound are not synthesized if the compound is present in the medium
-Common in biosynthetic pathways for AA's, purines, and pyrimidines |
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Induction
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The synthesis of enzymes only occurs when the compound used by the enzyme is present in the medium.
-Common in catabolic pathways for carbon and energy sources. |
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What types of molecules are likely to serve as co-repressors or inducers?
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-ArgR-arginine complex
-LacI -Lac-I Allolactose complex (Induction) |
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What molecules interact with ArgR and LacI and how are they classified?
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ArgR regulator is an allosteric protein that only binds DNA when the co-repressor (arginine) is bound. This complex binds to the operator site and blocks RNAP movement (repression)
LacI repressor is an allosteric protein that binds DNA in the absence of inducer. |
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What are the functions of an operator and a promoter in the initiation of transcription?
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Operator- is the DNA binding site for the regulator
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Regulon
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In some instances a regulatory protein controls the expression of multiple operons. This regulatory network is called a regulon.
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Constitutive
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-unregulated expression
ex: MalT activator does not bind to the activator site in the absence of the inducer. |