Micro Bio Lecture 18

Front 1

What are the two major modes of regulation in the cell? Which would be the quickest?

Back 1

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.

Front 2

What are the key features of an enzyme that is subject to allosteric regulation

Back 2

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.

Front 3

Feedback inhibition

Back 3

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.

Front 4

How is glutamine synthetase activity regulated by covalent modification?

Back 4

-It is regulated in part by covalent modification.

-The activity of Glutamine Synthetase decreases linearly with increasing modification

Front 5

Isozymes

Back 5

Multiple enzymes that carryout the same reaction, isozymes, and each isozyme is independantly regulated.

Front 6

How does intein removal differ from intron splicing?

Back 6

-Intein mediated protein splicing occurs Post-Translationallly

-Intron splicing occurs after transcription and before translation.

Front 7

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.

Back 7

-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

Front 8

Helix, Turn-Helix

Back 8

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.

Front 9

Zn-finger

Back 9

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

Front 10

Leucine Zippers

Back 10

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.

Front 11

Negative control of transcription

Back 11

1. Repression
2. Induction

Front 12

Repression

Back 12

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

Front 13

Induction

Back 13

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.

Front 14

What types of molecules are likely to serve as co-repressors or inducers?

Back 14

-ArgR-arginine complex
-LacI
-Lac-I Allolactose complex
(Induction)

Front 15

What molecules interact with ArgR and LacI and how are they classified?

Back 15

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.

Front 16

What are the functions of an operator and a promoter in the initiation of transcription?

Back 16

Operator- is the DNA binding site for the regulator

Front 17

Regulon

Back 17

In some instances a regulatory protein controls the expression of multiple operons. This regulatory network is called a regulon.

Front 18

Constitutive

Back 18

-unregulated expression

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