What is the role of the LacI protein?
Abstract. The lactose repressor protein (LacI), the prototype for genetic regulatory proteins, controls expression of lactose metabolic genes by binding to its cognate operator sequences in E. coli DNA.
What protein does LacI produce?
The LacI protein consists of two domains that bind the operator DNA and the inducer (N-terminal and core domain, respectively), a short C-terminal domain required for the formation of the homo-tetramer and a hinge region between DNA and inducer binding domains (Figure 1A)[25, 26].
What is the purpose of the protein coded for by the lacY gene?
The lacY gene encodes a permease that functions as a membrane-spanning transport protein to bring lactose into the cell, and the lacA gene encodes a transacetylase enzyme that transfers an acetyl group from acetyl CoA to beta-galactosidase.
What is the function of LacI in the regulation of the lac operon?
What is the function of lacI in the regulation of the lac operon? It is a structural gene that encodes permease. It is the promoter that mediates the transcription of the operon. It encodes a repressor that, in the absence of lactose, binds to the lac operator and blocks expression of the structural genes.
Does LacI have a promoter?
We previously introduced and characterized two LacI-regulated promoters, Ptrc[24] and Ptrc 2O, in the unicellular model cyanobacterium Synechocystis PCC 6803 (Synechocystis) [25]. Both promoters contain the same Ptrc core promoter, a chimera of the E.
Where does LacI bind to?
LacI, which is a tetramer, binds to O1 through two of its subunits. The other two subunits then bind either O2 or O3, forming a loop between the operators. Either configuration prevents the binding of RNA polymerase to the promoter.
Why is the lacI gene expressed without the help of an activator like CRP?
Because RNA polymerase has a high affinity for the PtrpR, the gene is expressed without requiring an activator protein. 26. How does glucose control expression of the lac operon? Low glucose levels increase cAMP levels.
What happens when lacI is mutated?
The lacI locus – One type of mutant allele of lacI (callled I-) prevents either the production of a repressor polypeptide or produces a polypeptide that cannot bind to the operator sequence. This is also a constitutive expresser of the lac operon because absence of repressor binding permits transcription.
What is LACL?
The lac repressor is a DNA-binding protein that inhibits the expression of genes coding for proteins involved in the metabolism of lactose in bacteria.
What happens to the expression of the lacI gene If lactose is not available in the cell?
What happens to the expression of the lacI gene if lactose is not available in the cell? There is no change—the lacI gene is constitutively expressed.
When the lac repressor protein binds to lactose why does it fall off its binding site at the operator?
If lactose is excluded from the cell, the lac operon cannot be induced. Since the operator is occupied with the repressor, the RNA polymerase cannot bind and transcribe these genes even when lactose is present.
What is the dominant allele for apples?
NOT 3:1 or 1:3. In apples, the alle le A is dominant for a big size apple and the allele R is dominant for red color. You cross one tree that produces big yellow apples and another tree that produces small red apples. Half of the offspring trees produce big red apples and half produce big yellow apples.
Why was DNA used in Hershey Chase?
DNA. In the Hershey-Chase experiment radioactive Sulfur was used to: Be incorporated into the phage protein coat because some amino acids contain sulfur. The experiments by Hershey and Chase helped confirm that DNA was the hereditary material on the basis of the finding that: Radioactive phosphorus was found inside the cell.
What is the genotype of a litter with 3 brown, 3 yellow, 1 black, 1 cream?
The genotype of parents of litters with the following phenotype distribution 3 brown, 3 yellow, 1 black, 1 cream is: BbDd x bbDd. In rats, gene B produces black coat color if the genotype is B-, but black pigment is not produced if the genotype is bb.
