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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?
1. Post-translational regulation
-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.
What are the key features of an enzyme that is subject to allosteric regulation
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.
Feedback inhibition
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.
How is glutamine synthetase activity regulated by covalent modification?
-It is regulated in part by covalent modification.

-The activity of Glutamine Synthetase decreases linearly with increasing modification
Multiple enzymes that carryout the same reaction, isozymes, and each isozyme is independantly regulated.
How does intein removal differ from intron splicing?
-Intein mediated protein splicing occurs Post-Translationallly

-Intron splicing occurs after transcription and before translation.
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.
-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
-Leucine Zipper
Helix, Turn-Helix
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.
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
Leucine Zippers
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.
Negative control of transcription
1. Repression
2. Induction
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
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.
What types of molecules are likely to serve as co-repressors or inducers?
-ArgR-arginine complex
-Lac-I Allolactose complex
What molecules interact with ArgR and LacI and how are they classified?
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.
What are the functions of an operator and a promoter in the initiation of transcription?
Operator- is the DNA binding site for the regulator
In some instances a regulatory protein controls the expression of multiple operons. This regulatory network is called a regulon.
-unregulated expression

ex: MalT activator does not bind to the activator site in the absence of the inducer.