Mimm 465 Lecture 12 Moual

Front 1

Types of secretion systems

Back 1

In both gram negative and gram positive:

1. General Sec pathway

2. Twin-arginine translocation

In gram +

Sortase(Attachment of proteins to cell wall)

In gram -

1. Type 1 to type 6 secretion system

2. Outer-membrane vesicles

Front 2

General secretory pathway

Back 2

1. translocation of unfolded protein that have N-terminal signal sequence.

2. Sec machinery is essential for bacterial viability

3. Sec consists of ATPase SecA and channel composed of SecE, SecY and SecG.

4. Translocation is powered by SecA ATP hydrolysis and proton motive force

5. signal peptide is cleaved by signal peptidase, mature protein released

Front 3

Twin-arginine translocation pathway

Back 3

1. TAT system transports fully folded protein (20 to 70 A). not presented in all bacteria.

2. Signal peptides used to target proteins to TAT contain twin-arginine motif

3. many protein containing non-covalently bound cofactors are secred through TAT

4. PMF provides energy

Front 4

Sortase

Back 4

1. all proteins secreted through Path but those with LPXTG motif at C terminus are recognized by Sortase (SrtA)

2. Sortase cleaves the protein between Thr and Gly and forms an amide bond between C-terminal Thr and lipid bilayer

Front 5

Type 1 secretion system

Back 5

1. family of multi-drug efflux system (e.g E. coli ArcB/ArcA/TolC system) BAC (cytoplasm to OM)

2. Type 1 SS is Sec independent, bypass the periplasm

3. tolC gene product functions with multiple transporters

4. Export of small molecules(antibiotics, detergent, dyes), bacterial toxins, enzymes

Front 6

Type 2 secretion system

Back 6

1. T2SS translocate fully folded proteins that passed through SEC or TAT Pathways

2. T2SS consists of 12 to 15 proteins designated as Gsp (General secretory pathway) mostly coded in one operon gsp.

3. OM complex is formed by dodecameric complex GspD

4. IM platform interacts with cytoplasmic ATPase (GspE) and periplasmic filamentous pseudopili

Front 7

Exotoxins vs Effector proteins

Back 7

1. Exotoxin: secreted outside of the cell and acts remotely

2. Effector protein: direcrly injected in host cell cytoplasm to initiate infection by type-3 and type 4 secretion system, independent of Sec.

Front 8

Type 3 secretion system

Back 8

similar to flagellar apparatus

1. Unfold effector proteins bind to chaperones to prevent aggregation

2. they are secreted through needle as unfolded proteins(about 13A, too small for folded)

3. Effector proteins fold in the host cell cytoplasm and modulate host cell pathways to promoter bacterial survival.

Front 9

Type 3 secretion system structure

Back 9

1. Translocon creates a pore in host cell membrane for delivery of effectors

2. basal structure is structurally related to flagellar body.

Front 10

Yersinia type 3 effector proteins

Back 10

1. YopH is a protein tyrosine phosphatase

2. YopE exerts GTPase-activationg proteing (GAP) activity on GTPases from rho

3. YopT cleaves GTPase close to their C terminus --> releasing them from membrane

4. YopO is a kinase with homology to Ser/Thr kinases that is activated by actin binding, binds ThoA and Rac1

Front 11

Type 4 secretion systems

Back 11

1. Versatile, Secrete a wide range of substrate (DNA, effector proteins)

2. Helicobacter pylori secretes single CagA effector through T4SS.

3. Leginonella pneumophila secretes up to 200 different effector proteins

Front 12

Type 5 secretion systems

Back 12

1. Autotransporters (like invasin of Yersinia enterolitica) use type 5 secretion system

2. Sec machinery dependent, proteins in periplasm then interact with chaperone

3. Chaperone-bound autotransporters are targeted to beta-barrel assembly complex (Bam complex) for insertion of beta-barrel domain into OM.

4. passenger domain translocated through Beta barrel

5. The autotransporters can then be cleaved resulting in secretion or not(bound to membrane)

6. cleavage can be by OM protease (lcsP), other transporters or autocatalytic

Front 13

Type 6 secretio nsystems

Back 13

1. Similar to contractile tail of bacteriophages (used to inject phage DNA)

2. Contact with a target cell induces contraction of outer tube (VipA/B) and pushes the inner tube (Hcp) and puncturing device (VgrG) through target cell

3. capable of injecting in both eukaryotic and prokaryotic cells, appears to be key to bacterial competition for colonization

Front 14

T6SS-mediated interbacterial antagonism

Back 14

1. T6SS of Pseudomonas aeruginosa exports 3 protein substrates (Tse1-3)

2. Tse2 protein is toxin component of toxin-immunity system Tse2/Tse1)

3. injection of Tse2 into P. aeruginose cells lacking Tsi2 results in growth arrest.

Front 15

OM vesicles

Back 15

1. OM of gram - bacteria blebs off to form round vesicles

2. released OM vesicles contain:

-periplasmic material

-OM proteins

-Lipids like LPS

-other PAMPS and virulence factors

3. budding occurs at places where lipoprotein links between OM and peptidoglycan are broke or missing

4. Increased vesiculation when encounters environmental stress.

Front 16

OM vesicles role in E. coli

Back 16

1. involved in interbacterial interaction (beneficial or antagonistic) and interaction with host cells

2. Enteretoxigenic E. coli(ETEC) produces heat-labile toxin (LT) uses OMV for delivery

3. LT is AB5 toxin that interacts with LPS and GM1 at host cell surface

Front 17

OMV in bacteroides fragilis

Back 17

1. B. fragilis releases PSA (polysaccharide A capsule) in OMVs

2. DC senses OMV-associated PSA through TLR2, resulting in increased Treg and antiinflammatory cytokines

3. prevent experimental colitis