L15 - Bacterial protein secretion and assembly of surface structures Flashcards
1
Q
What is the primary structural difference between Gram-positive and Gram-negative bacteria?
A
Gram-positive bacteria have a single membrane, while Gram-negative bacteria have both an inner and outer membrane.
2
Q
What are the two major secretion pathways used by Gram-positive bacteria?
A
Sec and Tat pathways.
3
Q
How does the Sec pathway function?
A
It transports unfolded proteins across the inner membrane using ATP hydrolysis.
4
Q
How does the Tat pathway function?
A
It transports folded proteins using the proton motive force.
5
Q
Which bacterial type (Gram-positive or Gram-negative) has more complex secretion systems?
A
Gram-negative bacteria
6
Q
Which secretion systems are exclusive to Gram-negative bacteria?
A
Type I, II, III, IV, V, and VI secretion systems.
7
Q
What is the role of the Sec and Tat pathways in Gram-negative bacteria?
A
They assist in protein transport before entering other secretion systems.
8
Q
What type of proteins does the Sec pathway transport?
A
Unfolded proteins.
9
Q
What type of energy does the Sec pathway require?
A
ATP hydrolysis.
10
Q
What happens to the signal peptide in the Sec pathway?
A
It is cleaved after translocation.
11
Q
What type of proteins does the Tat pathway transport?
A
Folded proteins.
12
Q
What energy source does the Tat pathway use?
A
Proton motive force.
13
Q
Which secretion system transports unfolded proteins and requires both a signal and translocator?
A
Type II secretion system.
14
Q
Which secretion system is known as the ‘autotransporter’ system?
A
Type V secretion system.
15
Q
What is the function of the Type III Secretion System (T3SS)?
A
It injects effector proteins directly into host cells like a syringe.
16
Q
How does the T3SS contribute to bacterial pathogenicity?
A
It manipulates host cell functions to favor bacterial survival.
17
Q
What is the role of the Type VI Secretion System (T6SS)?
A
It delivers proteins into neighboring bacterial cells for competition.
18
Q
How does the T6SS resemble the T3SS?
A
Both act as direct delivery mechanisms but have different targets.
19
Q
How do bacterial secretion systems aid infection?
A
They help bacteria evade host defenses and manipulate host cells.
20
Q
What are effector proteins?
A
Secreted bacterial proteins that alter host cell function.
21
Q
How can bacterial secretion systems be targeted therapeutically?
A
By designing drugs that block these pathways to reduce virulence.
22
Q
Why is research on secretion systems important for medicine?
A
It aids in developing new treatments for bacterial infections.
23
Q
What role do secretion systems play in antibiotic resistance?
A
They can help bacteria resist antibiotics by expelling drugs or modifying host responses.
24
Q
Why are animal models important in secretion system research?
A
They help assess bacterial pathogenicity and treatment efficacy.
25
How can bacterial structures be used in drug delivery?
They can be engineered to transport therapeutic molecules into cells.
26
What is the main characteristic of the Type I secretion system?
It transports proteins in a single step from the cytoplasm to the extracellular space.
27
What energy source does the T1SS use?
ATP-binding cassette (ABC) transporters.
28
Which bacterial species commonly use the T1SS?
Escherichia coli, Bordetella pertussis, Pseudomonas aeruginosa.
29
What is the role of the T2SS?
It transports folded proteins from the periplasm to the extracellular space.
30
What bacterial processes rely on the T2SS?
Toxin and enzyme secretion.
31
Which bacteria use the T3SS?
Salmonella, Shigella, Yersinia, Pseudomonas, E. coli.
32
Why is the T3SS important for bacterial virulence?
It allows direct injection of toxins into host cells.
33
What is a key feature of the T4SS?
It transports both proteins and DNA.
34
Which secretion system is used in bacterial conjugation?
Type IV secretion system.
35
Which pathogen uses T4SS for virulence?
Helicobacter pylori.
35
What is the unique feature of the T5SS?
The protein transports itself across the outer membrane.
36
What are the three subtypes of the T5SS?
Autotransporters, two-partner systems, and trimeric autotransporters.
37
What is the primary function of the T6SS?
It delivers toxins to competing bacteria.
38
How is the T6SS structurally related to another system?
It resembles a bacteriophage tail.
39
Which secretion system contributes to antibiotic resistance?
Type I secretion system (e.g., efflux pumps).
40
What secretion system is most associated with intracellular pathogens?
Type III secretion system.
41
Which system is used for DNA transfer between bacteria?
Type IV secretion system.
42
What secretion system uses a needle-like structure?
Type III secretion system.
43
Which secretion system can secrete folded proteins?
Type II secretion system.
44
Which secretion system is associated with biofilm formation?
Type V secretion system.
45
What secretion system is used by Vibrio cholerae?
Type II secretion system.
46
What secretion system is involved in bacterial competition?
Type VI secretion system.
47
What system does Pseudomonas aeruginosa use to secrete elastase?
Type II secretion system.
48
What secretion system is the main virulence factor in Yersinia pestis?
Type III secretion system.
49
What are the main functions of bacterial secretion systems?
They transport proteins and toxins essential for bacterial survival, communication, and infection.
50
How do bacterial secretion systems contribute to pathogenesis?
They allow bacteria to inject toxins, manipulate host cells, and evade immune defenses.
51
Why is the Sec pathway important for Gram-positive and Gram-negative bacteria?
It provides a pathway for transporting unfolded proteins across membranes.
52
What role does ATP hydrolysis play in bacterial secretion?
ATP hydrolysis drives the transport of proteins through the Sec pathway.
53
How does the Tat pathway differ from the Sec pathway?
The Tat pathway transports folded proteins and uses the proton motive force instead of ATP.
54
Which secretion systems require the Sec or Tat pathways for initial protein transport?
The Sec and Tat pathways assist in transporting proteins before they enter Type I–VI secretion systems.
55
How does the Type II secretion system transport proteins?
It moves proteins from the periplasm to the extracellular space using a translocator.
56
What makes the Type V secretion system unique?
It allows proteins to transport themselves across the outer membrane.
57
What is the main function of the Type III secretion system?
It injects effector proteins directly into host cells like a molecular syringe.
58
How does the Type III secretion system enhance bacterial virulence?
It enables bacteria to manipulate host cell processes to promote infection.
59
What is the structural similarity between the Type III and Type VI secretion systems?
Both systems use a needle-like apparatus for direct protein delivery.
60
How does the Type VI secretion system benefit bacteria?
It delivers toxins into competing bacteria, giving an advantage in microbial competition.
61
Which secretion system is most important in bacterial competition?
The Type VI secretion system is the primary system for interbacterial competition.
62
What role do effector proteins play in bacterial infections?
They alter host cell function to enhance bacterial survival and infection.
63
How can bacterial secretion systems be targeted for therapeutic interventions?
Drugs can be developed to block secretion system function, reducing bacterial virulence.
64
Why is research on bacterial secretion systems important for drug development?
It enables the design of new antibiotics and therapies targeting bacterial infections.
65
How do secretion systems help bacteria evade the host immune system?
They secrete proteins that interfere with immune detection and response.
66
Which bacterial secretion system resembles a bacteriophage tail?
The Type VI secretion system shares structural similarities with bacteriophage tails.
67
What is the significance of secretion systems in bacterial-host interactions?
They help bacteria establish infections by interacting with host cells and modifying their responses.
68
How can bacterial secretion systems be engineered for drug delivery?
Bacteria can be engineered to transport therapeutic molecules into target cells.
69
Which bacterial secretion systems are considered one-step systems in Gram-negative bacteria?
Type III, Type IV, and Type VI secretion systems directly span from the inner to the outer membrane without a periplasmic intermediate.
70
What is a defining feature of Type V secretion systems (autotransporters)?
The protein contains all information necessary for its own transport across the outer membrane.
71
What are the components of the Sec translocon complex?
SecA (ATPase), SecB (chaperone), and the SecYEG channel in the membrane.
72
How is protein translocation energized in the Sec pathway?
By ATP hydrolysis, with each ATP cycle pushing approximately 20 amino acids through the channel.
73
What sequence motif is required for protein recognition by the Tat pathway?
A twin-arginine motif: S/T-R-R-x-F-L-K, where x is any amino acid.
74
What triggers activation of the Type III secretion system?
Contact with a host cell triggers the T3SS to inject effector proteins into the host cytoplasm.
75
What is the function of the translocon in Type III secretion systems?
It forms a pore in the host membrane to allow injection of bacterial effector proteins.
76
What is a TPS system in Type Vb secretion?
Two-partner secretion, where one protein (TPSB) forms the pore and the other (TPSA) is the effector protein transported.
77
What is the role of TatA in the Tat secretion pathway?
TatA oligomerizes to form the translocation pore for folded protein export.
78
What kind of cellular processes can T3SS effectors manipulate in host cells?
They can alter actin cytoskeleton, modulate signaling, and facilitate bacterial uptake or adherence.
79
What is the role of lipoteichoic acid in Gram-positive bacterial envelopes?
Lipoteichoic acid anchors the cell wall to the membrane and may play roles in cell envelope stability and host interactions.
80
How does sortase A function in Gram-positive bacteria?
Sortase A cleaves specific protein motifs (e.g. LPXTG) and covalently attaches the proteins to the peptidoglycan.
81
Which proteins are often anchored to the Gram-positive cell wall via sortase enzymes?
Adhesins, invasins, and immune evasion proteins are often anchored via sortase enzymes.
82
What are LPXTG-motif proteins?
They are surface proteins with a conserved motif recognised and cleaved by sortase for cell wall anchoring.
83
What type of secretion system is used by Gram-positive bacteria to export sortase substrates?
The Sec pathway is used to translocate sortase substrates across the membrane.
84
Why are sortase-anchored proteins important for Gram-positive pathogens?
They mediate host interactions, including adhesion and immune evasion, contributing to virulence.
85
What role does the WXG100 protein family play in the Type VII secretion system?
WXG100 proteins are small, secreted proteins essential for the activity of Type VII secretion systems.
86
How is the Type VII secretion system different from Sec and Tat pathways?
The Type VII system secretes folded proteins across complex envelopes, unlike the Sec and Tat pathways.
87
Which bacteria primarily utilise the Type VII secretion system?
They are predominantly found in Actinobacteria, especially Mycobacterium species.
88
What is the role of ESAT-6 and CFP-10 in mycobacterial secretion?
They are secreted effectors involved in immune modulation and virulence.
89
How are ESX loci related to the Type VII secretion system?
ESX loci encode components and substrates of the Type VII secretion system.
90
Why is the Type VII secretion system important in Mycobacterium tuberculosis?
It is required for immune evasion and full virulence in host infection.
91
What is a common feature of Type VII secretion system substrates?
They typically contain a conserved WXG motif and form helical structures.
92
How is the function of the Type VII secretion system linked to virulence?
It enables bacterial survival and host manipulation during infection.
93
What structural feature allows Mycobacterium tuberculosis to require a specialised secretion system?
Its thick, lipid-rich envelope creates a need for specialised protein transport systems.
94
How are secretion systems classified in Mycobacterium tuberculosis?
They are grouped into ESX-1 to ESX-5 systems, each with different functions and substrates.
95
Why do Gram-positive bacteria not require outer membrane secretion systems?
Because they lack an outer membrane, their secretion ends at the peptidoglycan or extracellular environment.
96
What anchors surface proteins to the peptidoglycan layer in Gram-positive bacteria?
Through the action of sortase enzymes recognising specific protein motifs.
97
What is the consequence of sortase A deletion in pathogenic Gram-positive bacteria?
Loss of sortase A impairs virulence due to lack of surface protein anchoring.
98
What are the components of the ESX-1 secretion system?
The ESX-1 system includes core components like EccB, EccC, EccD, and EccE.
99
How are substrates recognised by the Type VII secretion system?
By specific C-terminal motifs and chaperone interactions with secretion machinery.
100
Which molecular motif is essential for substrate recognition in Type VII secretion systems?
The YxxxD/E motif helps direct substrates to the secretion machinery.
101
Why is the WXG motif important in ESAT-6-like proteins?
It helps mediate secretion and stabilise protein structure for export.
102
How do Mycobacteria ensure specificity of substrate secretion through ESX systems?
Through specific interactions between substrates and secretion system components.
103
Which secretion system is essential for full virulence of Staphylococcus aureus?
The sortase A system is essential for anchoring virulence factors to the surface.
104
What is the structural relationship between ESX systems and FtsK/SpoIIIE family proteins?
Both systems utilise AAA+ ATPases to drive protein transport through membranes.
