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27 Cards in this Set
- Front
- Back
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What are the three steps of protein synthesis?
How many IFs does bacteria have? Archea? |
initiation, elongation, termination
Bacteria: IF 1,2,3 Archea: 6 different IF's |
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In initiation, the initiating AA is BLANK or BLANK, which is specified by BLANK or BLANK. It also codes for...
In Archaea, the initiator tRNA is... |
N-formylmethionine, or fmet; AUG and GUG; fMet-tRNA
unmodified methionine |
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In protein synthesis, the initiation complex is formed from the binding of the BLANK ribosomal subunit to the BLANK codon, AUG or GUG on the mRNA.
In the 1960’s it was determined that BLANK % of all proteins in E.coli began with BLANK. |
30S; initiation
45%; methionine |
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In protein synthesis, the initiation codon establishes...
An initiator tRNA carrying fmet pairs with the initiation codon in the presence of the BLANK BLANK subunit and following the BLANK BLANK sequence. |
the reading frame for the mRNA
30S ribosomal subunit; Shine Dalgarno |
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In protein synthesis initiation, what is a purine rich region (3-9 bases) that precedes the 5’ end of the initiating AUG codon?
What does it specify? |
Shine Dalgarno sequence
it specifies the ribosomal binding site on the mRNA |
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Protein synthesis initiation requires a BLANK ribosomal subunit, BLANK, BLANK-tRNA and 3 protein initiation factors (LIST THEM) and BLANK.
What do the three initiation factors and GTP do? |
30S; mRNA; fmet-tRNA; IF1, IF2 and IF3; GTP
1. IF3, catalyzes the dissociation of the 70S ribosome into individual subunits; also binds 30S subunit to the appropriate site of the mRNA. 2. IF2 and GTP, involved in the positioning of the fmet-tRNA to the correct codon on the 30S subunit. 3. IF1 assists the IF3 in binding to the 30S subunit to the mRNA. |
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Protein synthesis elongation begins with the binding of an aminoacyl-tRNA to the BLANK BLANK on the mRNA at the BLANK site to determine the type of BLANK BLANK inserted into the protein.
Recognition requires 2 protein elongation factors BLANK and BLANK, and the hydrolysis of... What is their purpose? |
complementary codon; ribosomal; amino acid
EF-Ts (heat stable) and EF-Tu (heat unstable) and the hydrolysis of GTP to GDP + Pi These elongation factors promote the binding of incoming aminoacyl-tRNA molecules to the ribosome. |
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In protein synthesis elongation, in the growing peptide, the ribosome moves along the mRNA by one codon length in the 5’ to 3’ direction. This movement is called...
What other things does this movement require? |
translocation
it requires elongation factor “G” aka EF-G, and the hydrolysis of GTP. |
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In protein synthesis termination, protein synthesis continues until the ribosome reaches one of three nonsense (termination codons) on the mRNA which are....
Once read, a protein release factor (RF) binds the ribosome. E. coli has 3 RF’s which... The released protein still has the BLANK group on the methionine which has to be removed BLANK before it is truly free. |
UAA,UGA, UAG
hydrolyze the ester bond that holds the last tRNA that entered the ribosome. formyl;enzymatically |
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Protein synthesis: Summary
The mRNA is read in... A single mRNA can have several ribosomes attached to it (polyribosomes). This explains why... Translation BLANK to BLANK seconds for a growing bacterium to synthesize protein of BLANK to BLANK amino acids. |
the 5’ to 3’ direction.
little mRNA is required by cells for protein synthesis. 10 to 20; 300 to 400 |
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What two control mechanisms regulate protein synthesis?
Describe negative and positive transcriptional control. What antagonizes the negative control? |
negative regulation and positive regulation.
In negative transcriptional control, a repressor binds to DNA to inhibit transcription. In positive transcriptional control, an effector molecule binds to DNA to activate a promoter and promote transcription. An antagonist of the repressor is generally called an inducer, it allows initiation of transcription. |
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First model for transcriptional control of protein synthesis was the BLANK BLANK discovered in 1961 by...
This operon model is based on... An operon usually consists of 1 or more structural genes that are... Lac operon model is an example of a BLANK control system, and in the absence of activated repressor protein, there is... |
Operon Model; Jacob and Monod
lactose utilization in E. coli under the control of a common operator negative; enzyme synthesis |
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What are the 3 enzymes involved lactose uptake and utilization? Describe their jobs and what gene they are on.
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1. β galactosidase, which hydrolyzes lactose into glucose and galactose, (encoded on structural gene z).
2. β galactoside permease which transports the sugar into the cell, (encoded on structural gene y). 3. Thiogalactoside transacetylase, unknown function, (encoded on structural gene a). |
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What is a unit of transcription on the chromosome that consists of one or more structural genes under the control of a common operator?
The structural genes code for what 3 enzymes? |
Lactose operon (lac operon)
β galactosidase, β galactoside, Thiogalactoside transacetylase |
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In the lac operon, the operator is a region on the DNA that interacts with a repressor protein coded by...
Adjacent to the operator site within the operon is a promoter, where... The operator plays a key role in... |
the regulator gene also known as the i gene.
the RNA polymerase binds. transcription control. |
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What are the 6 genes on the lac operon? Describe them
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i p o z y a
Repressor(i) operator(o) promoter(p) structural genes: z,y,a |
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In the lac operon, the repressor attaches to the operator site to prevent...
The repressor can be inactivated by changing its configuration by the inducer, which is... Now the RNA polymerase is able to bind to the promoter region of the DNA and... |
binding of RNA polymerase to the promoter in the lactose operon.
lactose aka allolactose transcribe its structural genes within the operon. |
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The lac operon is not needed if...
The activity of the lac operon is regulated by... When bacteria grow on glucose... When bacteria are starved for carbon... So finally, what is a protein that positively regulates the lac operon? |
both glucose and lactose are present in the growth medium
cAMP level the cAMP level in the cells is low. the cAMP level is high. The cAMP receptor protein (CRP) |
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----In regards to cAMP aka CRP----
When E. coli is growing on glucose... E.coli-->BLANK-->BLANK cAMP activates numerous operons, of... cAMP controls expression of many genes by... cAMP-CRP binds to... |
it prevents synthesis of cAMP
E.coli-->glucose-->prevents synthesis of cAMP (catabolite repression) which lactose is one. binding with a dimeric regulatory protein (CRP). (Positive control mechanism). DNA sequences near bacterial genes |
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What is a constitutive enzyme? Describe this system
What is an example of this system? |
Constitutive enzymes are produced in constant amounts in the cell all the time; any system where the genes are continually transcribed.
Sulfur metabolism: grow on both organic and inorganic sulfur sources and then measure enzymatic levels produced. |
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What is an end product of a biosynthetic pathway that activates repressor proteins? This is an example of what control system?
The 5 structural genes trpE,D,C,B,A are regulated by what 3 things/regions? What corepressor do they need to help them regulate? |
Corepressor; negative control system
trpP,trpO,trpR; tryptophan (trp) from chorismic acid |
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On the topic of repression, the end product tryptophan increases the affinity of the repressor protein for the operator. Why is this and what is this an example of?
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The tryptophan (trp) acts a corepressor for the trpP, trpO, and trpR.
Example of feedback inhibition. |
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This regulation of transcription termination is called BLANK
Which region on lac operon controls termination? What does it contain? Where is it located? |
attenuation
trpL region; contains a stop signal aka attenuator; located on leader sequence |
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At low tryptophan levels, 2,3 stem loop forms and...
At normal or high levels, 3,4 stem loop forms and... |
tryptophan is made
tryptophan production is stopped |
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--Attenuation--
How does translation of the leader sequence regulate transcription of structural genes? |
The trp leader mRNA sequence can base pair in several alternative hairloop structures depending on the concentration of trp present.
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Catabolite repression is a positive control system. Name an example involving E. coli.
What type of growth does this lead to and what is it? |
E.coli, grown in the presence of lactose and glucose, the cells will first use glucose because it represses the lactose operon. The cells only use lactose when the glucose is gone, thus catabolite repression.
This leads to diauxic growth, a growth pattern in which there are 2 exponential phases of growth. |
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Why is it not good to grow bacteria with two food sources?
--------------- How is lactose/USP from diary byproducts used in drug manufacturing? |
Because of catabolite repression; in large scale fermentation you want to use one source like lactose
------------- Lactose is used to bind drugs; the active ingredient is compressed with lactose |
