Podcast
Questions and Answers
Which characteristic distinguishes Gram-negative bacteria secretion systems from those in Gram-positive bacteria?
Which characteristic distinguishes Gram-negative bacteria secretion systems from those in Gram-positive bacteria?
- Gram-negative bacteria utilize a simpler, single-step secretion mechanism.
- Gram-negative bacteria secretion systems are primarily Sec-dependent, unlike Gram-positive systems.
- Gram-negative bacteria require more complex secretion systems to traverse both the inner and outer membranes. (correct)
- Gram-negative bacteria possess less diverse secretion systems due to their thinner peptidoglycan layer.
What is the primary role of virulence factors that necessitate direct delivery into a host cell?
What is the primary role of virulence factors that necessitate direct delivery into a host cell?
- To trigger the host's immune response, leading to inflammation and tissue damage.
- To amplify their pathogenic effects inside the host cell, which may not be achievable extracellularly. (correct)
- To facilitate nutrient acquisition from the host's extracellular environment.
- To enhance bacterial motility and colonization within the host.
Secretion systems are categorized as Sec-dependent or Sec-independent. Which of the following secretion systems relies on the Sec machinery for initial protein translocation?
Secretion systems are categorized as Sec-dependent or Sec-independent. Which of the following secretion systems relies on the Sec machinery for initial protein translocation?
- Type III Secretion System (T3SS)
- Type II Secretion System (T2SS) (correct)
- Type I Secretion System (T1SS)
- Type IV Secretion System (T4SS)
The Sec system is crucial for general protein secretion in bacteria. What is the state of the proteins as they are transported through the SecYEG channel?
The Sec system is crucial for general protein secretion in bacteria. What is the state of the proteins as they are transported through the SecYEG channel?
Which component of the Sec system is responsible for binding to the signal sequence of nascent polypeptides and preventing their premature folding in the cytoplasm?
Which component of the Sec system is responsible for binding to the signal sequence of nascent polypeptides and preventing their premature folding in the cytoplasm?
The Twin Arginine Transport (Tat) system differs from the Sec system in its substrate specificity. What type of proteins are typically transported by the Tat system?
The Twin Arginine Transport (Tat) system differs from the Sec system in its substrate specificity. What type of proteins are typically transported by the Tat system?
Type II Secretion System (T2SS) is described as a 'pseudo pilus' system. What does this analogy refer to regarding its mechanism?
Type II Secretion System (T2SS) is described as a 'pseudo pilus' system. What does this analogy refer to regarding its mechanism?
Cholera toxin, an AB$_5$ toxin, is secreted by Vibrio cholerae using which secretion system?
Cholera toxin, an AB$_5$ toxin, is secreted by Vibrio cholerae using which secretion system?
Type V Secretion System (T5SS) is also known as the autotransporter system. What is the key feature that defines an autotransporter mechanism?
Type V Secretion System (T5SS) is also known as the autotransporter system. What is the key feature that defines an autotransporter mechanism?
In Type V Secretion System (T5SS), what is the role of the beta-barrel domain?
In Type V Secretion System (T5SS), what is the role of the beta-barrel domain?
VacA toxin from Helicobacter pylori is secreted via the Type V Secretion System (T5SS). What is a primary effect of VacA toxin on host cells?
VacA toxin from Helicobacter pylori is secreted via the Type V Secretion System (T5SS). What is a primary effect of VacA toxin on host cells?
The Bam complex is essential for the function of Type V Secretion System (T5SS). What is the role of the Bam complex in this process?
The Bam complex is essential for the function of Type V Secretion System (T5SS). What is the role of the Bam complex in this process?
Pertactin, a virulence factor of Bordetella pertussis, utilizes the Type V Secretion System (T5SS). How does Pertactin function in pathogenesis?
Pertactin, a virulence factor of Bordetella pertussis, utilizes the Type V Secretion System (T5SS). How does Pertactin function in pathogenesis?
Considering the Sec-dependent secretion pathways (Type II and Type V), what is the initial location of the protein after it has crossed the inner membrane?
Considering the Sec-dependent secretion pathways (Type II and Type V), what is the initial location of the protein after it has crossed the inner membrane?
Which of the following is a Sec-independent secretion system?
Which of the following is a Sec-independent secretion system?
Signal peptidases are enzymes that play a crucial role in the Sec pathway and lipoprotein biogenesis. What is their primary function?
Signal peptidases are enzymes that play a crucial role in the Sec pathway and lipoprotein biogenesis. What is their primary function?
Lipoprotein biogenesis in Gram-negative bacteria involves multiple steps. Which enzyme is responsible for the initial lipid modification of lipoproteins?
Lipoprotein biogenesis in Gram-negative bacteria involves multiple steps. Which enzyme is responsible for the initial lipid modification of lipoproteins?
The Lol pathway is specifically involved in the localization of lipoproteins in Gram-negative bacteria. Where are lipoproteins ultimately transported by the Lol pathway?
The Lol pathway is specifically involved in the localization of lipoproteins in Gram-negative bacteria. Where are lipoproteins ultimately transported by the Lol pathway?
Considering the signal sequence of Sec-dependent proteins, what is the typical length of the hydrophobic h-region within the signal peptide?
Considering the signal sequence of Sec-dependent proteins, what is the typical length of the hydrophobic h-region within the signal peptide?
What is a key advantage of evolving a secretion system that can inject proteins directly into host cells, compared to systems that secrete proteins into the extracellular environment?
What is a key advantage of evolving a secretion system that can inject proteins directly into host cells, compared to systems that secrete proteins into the extracellular environment?
Flashcards
Virulence Factor Delivery
Virulence Factor Delivery
Many virulence factors require direct delivery into a host cell to enhance their activity, making a delivery mechanism essential.
Gram-negative bacteria envelopes
Gram-negative bacteria envelopes
Gram-negative bacteria have more complex delivery systems because of their envelope structure with two membranes.
General Secretory System
General Secretory System
Proteins exit unfolded through this system, common to both Gram-positive and Gram-negative bacteria, using a 15 to 26 amino acid signal sequence.
Twin Arginine Transport System
Twin Arginine Transport System
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Secretion pathways in Gram-negative
Secretion pathways in Gram-negative
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Sec-Dependent Systems
Sec-Dependent Systems
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Type II Secretion System
Type II Secretion System
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Type V Secretion System
Type V Secretion System
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Bam Complex
Bam Complex
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Study Notes
- Bacterial secretion systems deliver virulence factors into host cells to potentiate their activity.
- Gram-negative bacteria possess more complex delivery systems due to their envelope structure.
General Secretory System
- Proteins exit unfolded through this system.
- Common to both Gram-positive (G+) and Gram-negative (G-) bacteria.
- Features a 15 to 26 amino acid signal sequence.
- SecB binds to the nascent peptide.
- SecA exhibits dimer ATPase activity.
- SecYEG forms a channel.
- SecDF-YajC stabilizes Sec.
- Cotranslation localizes proteins to the membrane.
Twin Arginine Transport System
- Transports folded proteins.
Lipoprotein Biogenesis
- Gram-negative bacteria have six pathways to transport proteins past the outer membrane.
- Two pathways depend on Sec or Tat to deliver proteins across the inner membrane (II and V).
- Four systems are Sec-independent (I, III, IV, and VI).
Sec-Dependent Systems
- Include Type 2 and Type 5 secretion systems.
Type II Secretion System (T2SS)
- Secretes some A-B toxins like Cholera and ExoA.
- Uses the general secretory or twin-arginine system to reach the periplasm.
- Proteins pass through a pore formed by 12 - 14 proteins.
- The mechanism is similar to pilin secretion, called "pseudo pili."
- Cholera toxin (AB5 complex) is secreted by type II.
Type V Secretion System (T5SS)
- Referred to as the autotransporter system.
- The single protein contains a protease domain (green), a passenger domain (blue), and a Beta-barrel domain (orange).
- Examples: Neisseria IgA Protease and Helicobacter VacA.
- The Beta domain threads into the outer membrane (OM) with the help of the Bam complex to create a Beta-barrel.
- The passenger and protease domain pass through the Beta-barrel to exit the cell.
- IgA protease self-cleaves to release the enzymatic active domain.
Bam Complex
- Bordetella Pertactin: The passenger and active domain remain attached to the OM and acts as an adhesin.
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