CMMB 343 - Final (Cell Communication)

Translocase systems

Moderate the transport of proteins using ATP, GTP, or PMF

Two universal translocases

Sec translocase (general secretion system) Tat translocase (Twin arginine translocase)

2 jobs of sec translocase system

1. Facilitates the cotranslation of membrane associated proteins into the cytoplasmic membrane (SRP mediated, uses GTP to power translocation). 2. Transports unfolded extracellular proteins into the cytosol (Sec-A mediated chaperone protein, uses ATP to power movement)

TAT (twin arginine translocase)

Transports folded extracellular proteins out of the cytosol (RR mediated twin arginine amino acids, uses PMF to power movement)

Two step translocases

Type II and V: Move proteins out of the cell one at a time

One-step translocases

Type I, III, IV, VI: Move proteins across membranes (or across the membrane of adjacent cells) in one step

T2SS

Sec or TAT move proteins across the inner membrane and then a second translocase moves folded proteins across the OM. Proteins attach to a secretion pore and are pushed out of the cell by ATP mediated pseudopili extension

TS22 is common for secretion of...

AB type toxins

T5SS

Sec moves autotransporter proteins across the inner membrane. The transporter domain of the autotransporter forms a pore in the OM for the passenger domain to exit the cell. Autoproteolysis separates the two domains

T5SS is common for the excretion of

exoenzymes (IgA protease), adhesins (pertactin), VacA cytotoxin

T1SS

ABC transporters that move proteins across both layers in one step. An inner membrane ABC transporter delivers proteins to a periplasmic membrane protein via ATP hydrolysis which pushes proteins out on an OM pore.

T1SS is common for secretion of...

bacteriocins, biofilm mediators (CApA), RTX toxins

T3SS

Transports proteins directly from the cytosol of the bacterial cell into the cytosol of a recipient cell (prokaryotic or eukaryotic). Found in both pathogens and symbionts. Upon contact with a recipient cell, the tip fuses with host membrane and proteins are moved using PMF

T3SS is common for transport of...

NOD factors or cytotoxins

T4SS

Transports proteins/DNA directly from the cytosol of the host cell into the cytosol of a recipient cell (prokaryotic/eukaryotic). Most common type of secretion system. ATP mediated

what kind of transfer systems does T4SS have

Conjugation systems: Responsible for the majority of HGT in prokaryotes. Used to transfer F plasmids and Ti plasmids Protein transport system: Transfers proteins into other cells or the extracellular space

T6SS

Transports proteins from the cytosol of a bacterial cell into the cytosol of a recipient cell (prokaryotic or eukaryotic) via an ATP-mediated T4 phage like injection system. When close to a target, contractile sheath proteins undergo a conformational change that extends the spike out of the donor cell into the recipient, delivering exoproteins

T6SS is used for...

Microbial warfare

Signals can act directly as effector molecules

Inducers bind to TFs (activators or repressors) and turn transcription on. Corepressors bind to repressors and turn transcription off.

Signals can act indirectly by...

Binding to cell surface receptors

Two component regulatory systems

Component 1 Sensor kinase: Transmembrane sensor kinase (histidine). With signal, they autophosphorylate using ATP and transfer signal (PO4) to a response regulator. Component 2 Response regulator: Uusally a TF that is active when phosphorylated. Component 3 Phosphatase: on the response regulator and removes PO4

Quorum sensing

Density dependent mechanism for cellular communication to induce a population or community response

What does quorum sensing regulate

Biofilm formation, sporulation, competence, bioluminescence, and production of virulence factors

quorum sensing is facilitated by

extracellular peptide or non-peptide signaling molecules (autoinducers) that accumulate as population density increases (when quorum is reached)

When a high enough concentration of a signal is reached...

coordinated gene regulation (at quorum)

acyl-homoserine lactone (AHL)

autoinducer molecule produced by many gram negative organisms; induces the expression of virulence genes

When cell densities are high, the AHL concentrations increase both ___________ and ___________ the cells

outside, inside

The AHL binds...

TF's, and some bind a sensor kinase

What does AHL binding result in?

Coordinated up-regulation of quorum specific genes, and some down-regulate genes

oligopeptide autoinducers (AIP)

Autoinducer molecule produced by gram-positive bacteria that regulate gene expression

How are Pre-AIPs transported?

Transported out of the cell (ABC transporters) into the surrounding environment

When the cell densities are high, the AIP concentration increases ____________ the cells

outside

What does AIP binding result in?

binds a sensor kinase, results in coordinated up-regulation and also down-regulation

Gram-positive and Gram-negative bacteria also produce autoinducers involved in...

interspecific quorum sensing

What is the best studied universal autoinducer? What does it result in? What are some examples of universal processes it is involved in?

AI-2: Results in coordinated upregulation of quorum specific genes across multiple species. Biofilm formation, HGT events, bacterial warfare are examples of universal processes

What are the structural variations of autoinducers?

Length of the acyl chain is 4-18C. R group can be OH, =O, H

6-12 aa acids is going to be an...

AIP

Bioluminescent bacteria can colonize the ________ ________ of marine creatures such as squid and flashlight fish

light organs

LuxI

A. fischeri express this at basal levels. It is an Acyl homoserine lactone synthase

3OC6-HSL

LuxI produces this AI-1-type AHL autoinducer

At high concentrations, 3OC6-HSL binds... (what does it do)

LuxR: an activator protein which binds to activator binding sites and induces the Lux operon. LuxR is regulated by an independent quorum sensing system.

Lux expression generates a...

positive feedback loop

LuxC, LuxD and LuxE produce

RCHO (long chain fatty aldehyde)

LuxA and LuxB produce

heterodimeric protein luciferase

LuxG produces

FMNH2 (a reduced electron carrier)

Luciferase produces light in the presence of

luciferin and O2

What is the mechanism for how luciferase produces light

RCHO + FMNH2 + O2 -> Light

S. aureus Global Control System

AgrD synthesized autoinducing peptide (AIP), AgrB exports AIP. At high concentrations, the AIP binds AgrC (signal kinase). AgrC phosphorylates AgrA (response regulator), and AgrA-P binds at activator binding sites within multiple regulons which upregulates the production of multiple virulence factors

Bacillus species produce...

Fengycin