Midterm 2

Question 1

Diphtheria toxin

Answer 1

Toxin catalyzes NAD ADP-ribosylating EF-2 (elongation factor 2)
Blocks prot syn
Diphthamide

Question 2

Diphthamide

Answer 2

Susceptible aa is extensively post-translationally modified histidine
EF-2
Diphtheria toxin

Question 3

Balifomycin

Answer 3

blocks vacuolar proton pump
prevents acidification of endosome
Prevent DT toxicity

Question 4

Anthrax toxin EF

Answer 4

Edema factor
Competitively binds to P63
Cleaves MAPK kinases –> no TNF
Triggers pyroptosis

Question 5

Anthrax toxin PA

Answer 5

Protective antigen
Necessary for activity of EF and LF
Binds to cellular receptor

Question 6

Anthrax toxin LF

Answer 6

Lethal Factor
Competitively binds to P63
Cleaves MAPK kinases –> no TNF
Triggers pyroptosis

Question 7

NALP1B (NLRP1)

Answer 7

Gene encoding inflammasome –> caspase-1 –> IL-1B
Activation of Nlrp1 –> pyroptosis
LF can be detected by NLRP1
LF sensitive mice (NlrP1+) are more resistant to spore
Protects against Bacillus anthracis infection
Human mphage are resistant to LT-induced pyroptosis –> v sensitive to spores

Question 8

LPXTG motif

Answer 8

• Gram + wall
• Sequence that anchors surface proteins to peptidoglycan at the C-terminus
• N-terminal signal sequence
• Followed by hydrophobic seq and charged tail
• Clipped by Sortase after secretion and covalently attached peptidoglycan

Question 9

Quellung rxn

Answer 9

Treated w Ab –> swelling of capsule. Add India ink–> ink is excluded by capsule

Question 10

Quorum sensing

Answer 10

• @ low densities surface prot for adherence to host tissues are expr
• @ higher densities, secrete virulence factors that kill host cells and facilitate spread of bac to new tissues and provide new food sources

Question 11

M-protein

Answer 11

• Surface exposed prot
• Primary target of IgG
• > 100 serologically distinct types
• LPXTG (mem anchor)
• Anti-phagocytic
• Ab to some M-prot cross react with mammalian prot

Question 12

Streptolysin O

Answer 12

SLO
Member of CDC family of hemolysins
Anti-SLO used to monitor infection by GAS
Can prevent chemotaxis of neutrophils
Can act as channel for intro of another secreted prot directly into host cells
Similarity to T3SS or B subunit

Question 13

sil locus

Answer 13

Evolution of S. pyogenes –> skin infection
silAB: two component regulatory system
silCR: encodes 17 aa quorum sensing pep
silDE: encodes ABC transporters

Question 14

Cholera toxin

Answer 14

AB5 toxin
Sec dependent
Secreted into and assembled in periplasm
Cell entry via retrograde translocation
Action: Catalyzes ADP-ribosylation rxn –> Transfers ADP-ribose from intracellular NAD to G-alpha –> ADP-ribosylated G-alpha is unable to hydrolyze GTP and thus remains active, stimulating adenylate cyclase resulting in incr of cAMP –> Causes large efflux of Na+ and H2O into gut lumen
Effects on immunity: Powerful immunogen –> anti-toxin Ab, Strong mucosal adjuvant, Blocks inflammation, Blocks inflammatory effects of TLR-activation in DC, Promotes DC IL-10 production (neg reg of innate immunity but promotes Ab production), Unintended consequence of stimulating acquired immunity to CT

Question 15

Cholera Toxin Co-regulated Pilus

Answer 15

Class IV pilus
Mediates attachment
TcpC encodes lipoprotein that confers serum resistance
TcpG is disulfide isomerase that catalyzes interchain disulfide bond in TcpA
ToxT, essential tx factor of TCP expression
ToxT and ToxR activate fusion

Question 16

Pertussis toxin

Answer 16

AB5 toxin
Action: ADP-ribosylation of a cysteine in the alpha subunit of an inhibitory trimeric G-protein (Gi) –> prevents the Gi complex from interacting with receptors, and so the complex remains bound to GDP and is unable to inhibit adenylyl cyclase –> PT has the same effect as CT although CT activates and PT prevents inhibition

Question 17

Filamentous Haemaglutinin

Answer 17

FHA
In Pertussis
 Surface prot
Ab target
Forms filamentous structures on bac surface that mediate adherence

Question 18

Pertactin

Answer 18

In pertussis
Surface prot
Ab target

Question 19

Tracheal cytotoxin

Answer 19

TCT
in pertussis
Produces respiratory epithelial cytopathology seen during disease
Stimulates NOD1
Induces IL-1 in resp epi cells –> induces NO –> toxicity
Blocks chemotaxis and neutrophils in neutrophils

Question 20

Adenylate cyclase

Answer 20

Pertussis
Produces cAMP only in presence of calmodulin
Single chain “AB toxin”
Adenylate cyclase mutants are 3-4 logs less virulent (intranasal neonate mice) –> similar to PT-/- mut
Renders phagocytes non-phagocytic and unable to kill

Question 21

T3SS

Answer 21

Present both in pertussis and bronchiseptica

Induces apoptosis in macrophages

Question 22

BvgS

Answer 22

Master regulator for coordinate gene reg
periplasmic sensor histidine kinase
Phosphorylates BvgA –> incr affinity for BvgA activated promoters

Question 23

BvgA

Answer 23

Master regulator for coordinate gene regulation

transcriptional activator

Question 24

Vrg

Answer 24

Bvg-repressed genes

Question 25

Vag

Answer 25

Bvg-activated gene

Question 26

Type IV pili

Answer 26

Bac aggregation, Adhesion to host cells, Twitching motility, Pilus retraction, DNA transformation, In other bac sp, gliding motility, In V. cholerae, TCP is CT phage receptor

Question 27

pilE

Answer 27

pilin Major pilus subunit, 20kDa Pilin is syn as precursor w signal seq processed by PilD Can switch b/w pilE1 and pilE2, incr variation

Question 28

pilD

Answer 28

Prepilin peptidase

Question 29

pilC

Answer 29

acts to counteract PilT mediated pilus retraction

Question 30

pilT

Answer 30

pilus retraction

Question 31

Gene regulation

Answer 31

Antigenic variation A specific gene can be expressed or repressed as a response to enviro stim BVG-regulated genes in Bordetella or ToxR-regulated genes in V. cholerae Temporal change in gene expression but no genome alteration

Question 32

Genetic variation

Answer 32

Antigenic variation For a subset of cells in a clonal pop, the genome is changes and gives rise to altered property Ex. Pilus structure and antigenicity May or may not be regulated, therefore may occur before bac are ever exposed to opsonic Ab that bind to pili

Question 33

pilS

Answer 33

silent gene | incr pilus variability

Question 34

Opacity

Answer 34

Outer mem prot Mediate bac-bac aggregation and close interations w cells 12 diff Opa proteins encoded on the chromosome Infec in human w Opa- bac results in emergence of Opa+ bac Turned on or off in individual cells at freq = 10-4 CTCTT (leader peptide) Codon following is CCG (Ser) has to be in frame to allow syn of leader pep to allow sec mediated export

Question 35

Cytochalasin D

Answer 35

Blocks actin polymerization

Question 36

Inv

Answer 36

Outer mem prot Sufficient to confer invasive phenotype on E.coli K12 Expr @ low T Incr expr at low pH consistent w role during initial stages of infection

Question 37

Invasin

Answer 37

Bac surface prot | Binding to fibronectin receptor w high affinity triggers zipper mediated internalization

Question 38

Gentamicin

Answer 38

Prevents Yop expr | Stops prot syn by binding to ribosome

Question 39

Yops

Answer 39

``` Syn relate to [Ca2+] and T Secreted into cells Inhibits phagocytosis in macrophages Inhibits internalization in HeLa cells Inhibits respiratory burst in neutrophils and macrophages Inhibits cytokine expr (YopJ) Block pyroptosis (YopM) Promotes cell rounding and dissolution of focal adhesions and stress fibers (Yop H) ```

Question 40

YopJ

Answer 40

Inhibits cytokine expr Plasmid-encode type II translocated effector Appears to block immune signalling by adding acetyl group to kinases in MAP kinase or NF-kB pathways (inactivates)

Question 41

YopM

Answer 41

Type III translocated effector Blocks pyroptosis Stim PRK-phosphorylation of Pyrin (inactivates)

Question 42

YopH

Answer 42

Promotes cell rounding and dissolution of focal adhesions and stress fibers

Question 43

YopE

Answer 43

Type II translocated effector Block phagocytosis RhoGAP that inactivates Rho GTPases Responsible for pyrin activation

Question 44

YopT

Answer 44

Type II translocated effector Blocks phagocytosis Protease that cleaves and inactivates Rho GTPases Resp for pyrin activation