5- Chapter 6 Flashcards
What are the two major approaches cells use to regulate protein function?
One controls the amount of an enzyme or other protein
The other controls the activity of a performed enzyme or other protein
What is gene expression?
The processes that regulate the amount of protein synthesized at the level of transcription, or by varying the amount of mRNA made, or at the level of translation
What is the main site of protein binding on DNA?
What is a protein domain?
The major groove of DNA
To achieve high specificity, the binding protein must interact simultaneously with several nucleotides
Protein domain is regions of the protein with a specific structure and function
What is the most common protein domain structure critical for proper binding to DNA?
Helix-turn-helix structure that consists of 2 segments of polypeptide that have alpha helix connected by a short sequence forming a turn
First helix is recognition helix, interacts with DNA
Second helix is stabilizing helix that stabilizes the first helix by using hydrophobic interactions
Page 175 diagram
What is negative control of transcription?
What is repression and induction?
It is a control that prevents transcription
Repression is where the enzymes that catalyze a product are not made if the product is already in the medium (shuts off pathways)
Induction is the opposite where an enzyme is only made when the product is present (turns on pathways)
Genes that are negatively controlled haveba default of ON
Look at graphs of induction and repression on page 176
What are inducers and corepressors?
Inducers- substance that induces enzyme synthesis (loss of repression)
Corepressors- substance that represses enzyme synthesis
These are both effectors and are normal cell metabolites
They affect transcription by binding to specific DNA binding molecules
Diagram on page 177
What is a repressor protein?
What arginine (corepressor or inducer) binds to
It is allosteric which means it’s confirmation is altered when the effector molecule binds to it
Repressor protein is activated when effector binds to it
Picture on 177
What is the operator and operon?
What is a regulon?
Operator is the specific region of the DNA near the promoter of the gene where the repressor protein binds
Operon is a cluster of consecutive genes who’s expression is under the control of a single operator
When more than one operon is under the control of a single regulatory protein, these operons are called a regulon
Pictures on 177
What is positive control of transcription?
The regulatory protein activates the binding of rna polymerase to dna
Binds activator protein to DNA which allows RNA polymerase to begin transcription
Genes that are positively controlled have a default OFF
If proteins that regulate the expression of the gene are removed, the gene would not be expressed
What is catabolite repression?
What is a downside if this
Is an extreme example of global control (regulate expression of many different genes simultaneously)
That control the use of carbon sources of more than one is present (best carbon is used first)
Lac operon is under control of this (uses positive and negative control)
Downside is it might lead to two exponential growth phases called diauxic growth
Graph on page 180
What is cyclic AMP and Cyclic AMP receptor protein?
Cyclic AMP receptor protein is the positively controlled activator protein that catabolite repression depends on
Cyclic AMP is a key molecule in many metabolic control systems (only made when cell is low on glucose) and is a regulatory nucleotide
How is transcription controlled in archaea?
Archaea use DNA binding proteins to control transcription and have both types of regulatory proteins
Example of repressor protein is NrpR protein
Diagram on page 181
Some arachael regulators can work as both a repressor and an activator (dusk functionality)
What are two component regulatory systems?
Single transduction systems with two parts
2 proteins: sensor kinase (detects environmental signal
Response regulator (DNA binding protein regulates transcription)
Contains a feedback loop
Almost 50 different ones in E. coli
Some signal transduction systems have multiple regulatory elements
What are phosphatases and what is their role?
The feedback loop employs a phosphatase which is an enzyme that removes the phosphate from the response regulator at a constant rate in two component regulator systems
Picture on page 183
How does chemotaxis use two component systems?
It uses modified two component systems to sense temporal changes in attractants or repellents and process this information to regulate the direction of flagellate rotation
Several sensory proteins sit in membrane and sense attractants or repellents
