Biochemistry
6th Edition
ISBN: 9781305577206
Author: Reginald H. Garrett, Charles M. Grisham
Publisher: Cengage Learning
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Chapter 29, Problem 10P
Interpretation Introduction
Interpretation:
To predict if the lap repressor interaction with inducer would be cooperative and, specify if it would be advantageous for the inducer to have cooperative binding to lac repressor.
Concept introduction:
DNA or Deoxyribonucleic acid is a molecule made of two chains which coil around one another. These form a double helix which carries instructions genetical in nature like related to reproduction, growth, development, functioning of the living organisms.
Lac operon repressor is homotetramer. The arrangement is such that this acts as a dimer’s dimer making the repressor bind to 2 separate operators.
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Explain the energetics and kinetics of specific binding between DNA and the lac Repressor
Answer as Directed. Below is the model of a lac operon.
lac I
lac Z
с
promoter operator
lac Y
lac A
DNA
+1
1. What are structural genes? Are the lac structural genes transcribed in the absence of
lactose?
2. What is the role of the promoter and operator sites in the operon?
3. Is the repressor protein bound to the operator site in the absence of lactose? In its
absence?
4. Under what nutritional circumstances (high or low glucose) is CAP bound to cAMP?
5. In the absence of lactose and the presence of glucose in the bacterial growth media,
what proteins are bound to the lac control region? Is the operon being transcribed then?
6. In the presence of lactose and the presence of glucose in the bacterial growth media,
what proteins are bound to the lac regulatory region? Is the operon being transcribed
then?
7. In the presence of lactose and the absence of glucose in the bacterial growth media,
what proteins are bound to the lac control region?
8. Why is it adaptive for a bacterium to not…
Direct mutagenesis of Ca2+ ATPase gene resulted in the replacement of two amino acid residues - Asn111 and Asn114 to Ala. These substitutions led to the reduction in Ca2+ transport activity by 10% and 50%, respectively. On the other hand, directed mutagenesis that resulted in the alteration of four Glu residues in the lumenal loop of this transport protein to Ala, did not affect the Ca2+ transport. Provide the possible explanation for the observed differences in the Ca2+ transport activity between the protein with Asn->Ala substitution and the protein with Glu->Ala substitution.
Chapter 29 Solutions
Biochemistry
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Ch. 29 - Post-transcriptional Modification of Eukaryotic...Ch. 29 - Prob. 12PCh. 29 - Prob. 13PCh. 29 - The Lariat Intermediate in RNA Splicing Draw the...Ch. 29 - Prob. 15PCh. 29 - Prob. 16PCh. 29 - Prob. 17PCh. 29 - Prob. 18PCh. 29 - Figure 29.15 highlights in red the DNA phosphate...Ch. 29 - Chromatin decompaction is a preliminary step in...
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- Answer as Directed. Below is the model of a lac operon. lac I lac Z с promoter operator +1 lac Y lac A DNA 1. In the absence of lactose and the presence of glucose in the bacterial growth media, what proteins are bound to the lac control region? Is the operon being transcribed then? 2. In the presence of lactose and the presence of glucose in the bacterial growth media, what proteins are bound to the lac regulatory region? Is the operon being transcribed then? 3. In the presence of lactose and the absence of glucose in the bacterial growth media, what proteins are bound to the lac control region? 4. Why is it adaptive for a bacterium to not express the genes that encode for that lactose utilization proteins when lactose is not available or when glucose is present? 5. Why is it adaptive for the structural genes for using lactose to be under the control of a single promoter, i.e., synthesize a polycistronic message rather than three monocistronic message?arrow_forwardNow read this abstract from a 2013 journal article What is the authors' explanation of how Gal80p works? Note UASG from the question above is the same as UASGAL The DNA-binding transcriptional activator Gal4 and its regulators Gal80 and Gal3 constitute a galactose-responsive switch for the GAL genes of Saccharomyces cerevisiae. Gal4 binds to GAL gene UASGAL. (upstream activation sequence in GAL gene pro- moter) sites as a dimer via its N-terminal domain and activates transcription via a C-terminal transcription activation domain (AD). In the absence of galactose, a Gal80 dimer binds to a dimer of Gal4, masking the Gal4AD. Galactose triggers Gal3-Gal80 interaction to rapidly initiate Gal4-mediated transcription activation. Just how Gal3 alters Gal80 to relieve Gals0 inhibition of Gal4 has been unknown, but previous analyses of Gal80 mutants suggested a possible competition between Gal3-Gal80 and Gal80 self-association interactions. Here we assayed Gal80-Gal80 interactions and tested for…arrow_forwardIn terms of the efficient use of bacterial resources, explain why it is necessary for lac operon expression to be controlled both by the lac repressor and by a cyclic AMP receptor protein rather than just by the lac repressor alone.arrow_forward
- The diagram below shows a closeup of regulatory proteins binding to one of the UASG elements near the GAL7, GALI0, and GALI genes, which code for the protein products needed for yeast to use the sugar galactose. The red triangle symbolizes an "effector" molecule that binds to Gal80p. In this hypothesis (which has since been shown to be incorrect), what could be happening to Gal80p when it is bound to the effector molecule that causes it to change its position and uncover the Gal4p transcriptional activation domain. Hint: think about what effector molecules do upon binding to proteins such as the the Lac repressor protein or the CAP protein. Galactose absent, glucose absent Gal80p. _Activation domain Gal4p dimer -Binding domain UASG Galactose present, glucose absent Activation domain Gal80p- Binding domain UASG For the toolbar, press ALT+F10 (PC) or ALT+FN+F10 (Mac).arrow_forwardSearching the yeast Saccharomyces cerevisiae genome, researchers found approximately 4,000 DNA sites with a sequence which could potentially bind the yeast transcription factor GAL4. GAL4 activates the transcription of galactose genes. Yet there are only 10 GAL4-binding sites which control the genes necessary for galactose metabolism. The GAL4 binding sequence is CGGAT#AGAAGC*GCCG, where # is T, C or G, and * is C or T. In one chromatin immunoprecipitation experiment (ChIP), yeast growing on galactose were lysed, and subjected to cross-linking reagents which cross-linked transcription factors and activators to DNA. Next the DNA was sheared into small fragments, and antibodies to GAL4 were added. These antibodies coprecipitated the GAL4 and the DNA it was cross-linked to. The cross-linking was then chemically reversed, and the DNA was isolated, cloned into a library of plasmids and sequenced. Results showed that only 10 different DNA sequences had GAL4 bound. Since the…arrow_forwardRead aloud V Draw Highlight 2. You are studying the regulation of the lactose operon in Escherichia coli, by measuring expression of the lacZ gene (i.e production of beta-galactosidase). (a) You identify several loss-of-function mutations in which lacZ is never expressed, in the presence and absence of glucose and lactose. What components of the lac operon could be mutated to produce this phenotype? List all possibilities. (b) You identify another loss-of-function mutation with the following expression pattern: Media + glucose - lactose + glucose +lactose - glucose - lactose - glucose + lactose lacZ expression Low Low High High What components of the lac operon could be mutated to produce this phenotype? List all possibilities.arrow_forward
- Predict the level of genetic activity of the lac operon as well as the status of the lac repressor and the CAP protein under the cellular conditions listed in the accompanying table. Lactose Glucose (a) - - (b) + - (c) - + (d) + +arrow_forwardExplain why (a) inactivation of the O2 or O3 sequence of the lac operon causes only a twofold loss in repression, and (b) inactivation of both O2 and O3 reduces repression ∼70-fold.arrow_forward. Recall that the trp operon has a special leader sequence (trpL) between the operator and the structural genes that offers attenuation as a mechanism for regulation of gene expression. (A) Draw a diagram of a trpL region of the operon when tryptophan is abundant in the cell.Label the following features: the DNA, 5’ and 3’ polarity of the RNA, the regions 1, 2, 3,and 4 and poly-U of the RNA, the pair of Trp codons (UGG), the ribosome, and RNA-Pol,along with any stem-loop structure that would form under these conditions (B) In the above example, will the rest of the trp operon genes be expressed? Briefly describe your reasoning why or why not (C) The trp codons in region 1 of the trpL gene have mutated to cysteines (UGG to UGC). What will be the effect on attenuation gene regulation of the trp operon? Brieflyexplain your reasoning.arrow_forward
- Plz answer ASAP. I will thumb up You are studying the regulation of the lactose operon in Escherichia coli, by measuring expression of the lacZ gene (i.e production of beta-galactosidase).(a) You identify several loss-of-function mutations in which lacZ is never expressed, in the presence and absence of glucose and lactose. What components of the lac operon could be mutated to produce this phenotype? List all possibilities.arrow_forward. An interesting mutation in lacI results in repressorswith 110-fold increased binding to both operator andnonoperator DNA. These repressors display a “reverse”induction curve, allowing β-galactosidase synthesis inthe absence of an inducer (IPTG) but partly repressingβ-galactosidase expression in the presence of IPTG. Howcan you explain this? (Note that, when IPTG binds a repressor, it does not completely destroy operator affinity,but rather it reduces affinity 110-fold. Additionally, ascells divide and new operators are generated by thesynthesis of daughter strands, the repressor must findthe new operators by searching along the DNA, rapidlybinding to nonoperator sequences and dissociating fromthem.)arrow_forwardSome elongation factors are evolutionarily related to the G-proteins involved in signal transduction. Provide a possible reason why this is the case.arrow_forward
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