What does ppGpp regulate?
Regulation of general metabolism by (p)ppGpp is exerted by its action on multiple processes: first, at the level of transcription, (p)ppGpp controls the expression of genes involved in amino acid biosynthesis5; second, it regulates nucleotide metabolism by binding directly to the enzymes involved in nucleotide …
Is ppGpp a protein?
This protein also has the capacity to synthesize (p)ppGpp, and seems to be the primary synthase under certain conditions of stress. Most other bacteria encode a single protein that is responsible for both synthesis and degradation of (p)ppGpp, generally homologs of SpoT.
What do Alarmones do?
An alarmone is an intracellular signal molecule that is produced in bacteria, chloroplasts, and a slim minority of archaea reacting to harsh environmental factors. They regulate the gene expression at transcription level.
What does stringent response do?
The stringent response, also called stringent control, is a stress response that occurs in bacteria and plant chloroplasts in reaction to amino-acid starvation, fatty acid limitation, iron limitation, heat shock, and other stress conditions.
What is the effect of rifamycin on transcription?
Rifamycin inhibits translation but has no effect on transcription.
How do riboswitches work?
Riboswitches are structured mRNA elements involved in gene regulation that respond to the intracellular concentration of specific small molecules. Binding of their cognate ligand is thought to elicit a global conformational change of the riboswitch, in addition to modulating the fine structure of the binding site.
How is ppGpp produced?
(p)ppGpp orchestrates the stringent response (SR) in bacteria; thus, it is produced during nutrient stress (such as amino acid or fatty acid starvation) by proteins belonging to the RelA/SpoT homolog family (RSH) (16).
What is guanosine tetraphosphate?
Guanosine tetraphosphate is a guanine nucleotide containing four phosphate groups. Two phosphate groups are esterified to the sugar moiety in the 5′ position and the other two in the 2′ or 3′ position.
What is stringent factor?
The stringent factor RelA binds to blocked ribosomes and catalyzes synthesis of (p)ppGpp, a secondary messenger that induces the stringent response. We demonstrate that binding of RelA and (p)ppGpp synthesis are inversely coupled, i.e., (p)ppGpp synthesis decreases the affinity of RelA for the ribosome.
How is RelA used in the stringent response?
RelA mainly responds to amino acid starvation, while SpoT responds to other starvation conditions. The ‘stringent response’ encompasses an inhibition of several other cellular processes and in several bacteria it is involved in modifying the expression of QS genes in a low nutrient environment.
What is the mechanism of action of rifampicin?
Mechanism of action — Rifampin is thought to inhibit bacterial DNA-dependent RNA polymerase, which appears to occur as a result of drug binding in the polymerase subunit deep within the DNA/RNA channel, facilitating direct blocking of the elongating RNA [6]. This effect is thought to be concentration related [7].
How do rifamycins work?
Rifamycin is used to treat of travelers’ diarrhea caused by certain bacteria. Rifamycin is in a class of medications called antibiotics. It works by stopping the growth of the bacteria that cause diarrhea. Antibiotics such as rifamycin will not work for colds, flu, or other viral infections.
What are riboswitches and its role?
The riboswitch is a part of an mRNA molecule that can bind and target small target molecules. An mRNA molecule may contain a riboswitch that directly regulates its own expression. The riboswitch displays the ability to regulate RNA by responding to concentrations of its target molecule.
How do riboswitches control protein production?
Currently, some of the most common mechanisms for riboswitch-mediated gene control involve the direct regulation of translation initiation, or the inhibition of protein production more indirectly by altering mRNA stability or by changing the primary sequence of mRNAs via alternative splicing.
What is GTP biology?
Definition of GTP
: an energy-rich nucleotide analogous to ATP that is composed of guanine, ribose, and three phosphate groups and is necessary for peptide-bond formation during protein synthesis. — called also guanosine triphosphate.
Which genes are activated during the stringent response and why?
Both lasR and rhlR gene expression and autoinducer synthesis were prematurely activated during the stringent response induced by overexpression of relA.
What process does rifampicin inhibit?
Abstract. Rifampin specifically inhibits bacterial RNA polymerase, the enzyme responsible for DNA transcription, by forming a stable drug-enzyme complex with a binding constant of 10(-9) M at 37 C.
How does rifampicin inhibit transcription?
Rifampicin binds to the exit channel of the RNA polymerase by making specific contacts that involve the β-subunit of RNA polymerase. Rifampicin blocks the exit channel thereby inhibiting transcription (Campbell et al., 2001).
What is role of rifamycin in transcription?
Rifampin specifically inhibits bacterial RNA polymerase, the enzyme responsible for DNA transcription, by forming a stable drug-enzyme complex with a binding constant of 10(-9) M at 37 C. The corresponding mammalian enzymes are not affected by rifampin.
How does rifamycin prevent microbial growth?
The drug works by blocking the path of the elongating RNA when the transcript reaches two to three nucleotides in length. Resistance to rifamycins can occur frequently, and is mainly due to point mutations in the rifamycin-binding region of the β subunit of RNAP.
What are riboswitches examples?
Examples of riboswitch ligands include glycine, coenzyme B12, thiamine, flavin mononucleotides, S-adenosylmethionine, and guanine. As such, riboswitches represent unique target opportunities for drugs.
What is the function of riboswitches?
Why are riboswitches important?
This region of the P1 helix is the switching sequence (Figure 1, purple). These additional ligand-induced interactions with the P1 helix stabilize its incorporation into the aptamer domain. Why is this important? It prevents the helix from being utilized to form alternative structures in the expression platform.
What is the role of GTP in protein synthesis?
GTP is used in protein synthesis. During initiation of translation, the GTP is associated with an initiation factor 2 (IF2) and is hydrolyzed upon the assembly of the initiation ribosomal complex. During elongation, GTP facilitates the binding of a new aminoacyl tRNA to the A site of a ribosome.
Is GTP same as ATP?
The key difference between ATP and GTP is that ATP is a nucleoside triphosphate made up of adenine nitrogenous base, sugar ribose, and triphosphate, while GTP is a nucleoside triphosphate made up of guanine nitrogenous base, sugar ribose, and triphosphate.