Quiz 04/13/23 Flashcards
what does the trp operon encode?
enzymes that are involved with the biosynthesis of tryptophan
trp is a _________ operon, which means it can be repressed by the presence of a particular substance
repressible
How many continuous structural genes are in a trp operon and what are they?
- 5
- TrpE, D, C, B, and A gene
Structural genes of a trp operon transcribe what type of mRNA?
Polycistronic mRNA
What enzyme is created from the genes of the trp operon?
tryptophansythetase
What are the regulatory and repressor genes of the trp operon? (4 total)
- Promoter region (P)
- Operator region (O)
- trpL gene
- Attenuator region
What are the functions of the trpL gene of the trp operon?
- Encodes leader peptide (14 amino acids)
- The mRNA determines the transcription and translation of the trp operon
What is the function of the attenuator region of the trp operon?
When tryptophan is present, the attenuator region of the trp operon encodes immature transcription
What is the function of the trpR gene? (which is upstream of the trp operon)
It produces repressors that bind to the operator region
Summarize the trp operon model (hint: talk about tryptophan)
- The presence of tryptophan determines whether or not the gene is expressed
a. No/low tryptophan, repressor is inactive, can’t bind to operator region –> gene is expressed
b. Tryptophan present, repressor is active, repressor binds to operator region –> gene is NOT expressed
-Also, when present, attenuation occurs and a stem-loop is formed, causing premature termination of transcription
-Charged trp-tRNA present
-Production of tryptophan is stopped
-INCOMPLETE CARD
In an operon, catabolic verses anabolic genes are usually regulated in what kind of manner?
- Catabolic- inducible manner
- anabolic- repressible manner
The majority of gene regulation in bacteria is at a ___________ level
transcriptional, although posttranslational is also possible
In translational regulation, the repressors have three characteristics. What are they?
Repressors:
1. Have sequence within mRNA
2. May bind to Shine-Dalgarno sequence
3. Binding may cause structural change on mRNA
In translational regulation, the antisense RNA is…
- complementary to mRNA
- does osmoregulation in E. coli
Which gene in the osmoregulation of E. coli forms porins on the outer membrane of E. coli?
ompF gene
What do porins control?
- Osmotic pressure of the cell
What do proin plugs do?
Keep solutes from going INTO the cell
Which gene inhibits porin formation?
micF gene
What type of condition outside the cell allows for the solutes to flow inside the cell?
hypotonic condition
The RNA of the micF gene is antisense to which mRNA?
ompF mRNA
Does the micF gene produce protein?
No
What are the 4 points in feedback inhibition during post-translational regulation?
- The final product of the pathway inhibits activity of one or more enzymes of the pathway
- The enzymes have a regulatory, allosteric, and a catalytic site
- The binding of the final product to regulatory site changes shape of enzyme
- The enzyme cannot bind to substrate
During post-translational regulation, the covalent modification of enzymes are done in which three ways? And which modifications are reversible?
- Modification may include:
a.) proteolytic processing
b.) disulfide processing
c.) attachment of sugars, functional groups, or lipids - Reversible modifications are:
a.) phosphorylation
b.) acetylation
c.) methylation
What year were riboswitches discovered?
2001 and 2002
A riboswitch can mediate RNA function. How?
A small molecule binds to a regulatory segment of mRNA, which causes conformational change, which leads to the change of mRNA function
Riboswitches of mRNA regulates its own _____________ and ________________
translational activity, enzymatic activity
What organisms are riboswitches found in?
Bacteria, archaea, algae, fungi, plants
What are the types of riboswitches (Table 14.2)
Table 14.2
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ESSAY QUESTION
During transcription of riboswitches, what type of hairpins are formed?
rho-independent transcription termination hairpins
Regulation of transcription and translation via riboswitches is governed by which compound?
Thiamin pyrophosphate (TTP)
What is Thiamin pyrophosphate (TTP)?
An essential coenzyme for the functioning of various enzymes
-Also called vitamin B
Describe the transcriptional control of thi operon of B. subtilis bacteria (HINT: Talk about TTP/VIT B)
-When TPP is LOW, ‘terminator step loop’ cant form because of the formation of a secondary structure called ‘antiterminator’ prevents termination, which completes transcription.
-When TPP is HIGH, TPP will bind to the thi operon mRNA that is being transcribed, which causes the mRNA to change it’s secondary structure, forming a ‘terminator stem loop’, which stops transcription.
Describe the translational control of thiMD operon in E. coli. (HINT: TPP) Also, how many enzymes are encoded and what is their purpose?
- When TPP levels are LOW, the 5’ end of mRNA folds into a secondary structure, the Shine-Dalgarno sequence is accessible to ribosomes, and translation is completed.
-When TPP levels are high, TPP binds to the 5’ end of the mRNA and causes a change in the secondary structure. The Shine-Dalgarno sequence is no longer accessible to the ribosome and translation is stopped - Two enzymes are encoded and are involved with TPP biosynthesis
