Bacterial secretion mechanism L10 Flashcards
importance of secreting proteins
have key role in modulating bacterial interactions in their environment
modifying host physiology for bacterial survival and promoting of colonisation of host
secretion systems
these proteins export machinery outside cells and inside other cells
different types depend
plays role in virulence, communication, metabolism ect
SEC - secretion system
general secretion type
found everywhere and essential, main route for protein export and require signal peptide/leader sequence
translocates unfolded proteins and needs ATP
TAT secretion systems
twin-arginine translocation
not as widespread
normally transports fewer substrates than SEC
translocates folded proteins and requires the proton motive force for movement
one step secretion
from cytoplasm to extracellular environment or target location directly, one step
T1 and T3 are examples
- seen common in gram +ve and sometimes in gram -ve
two step secretion systems
intermediate step from cytoplasm to periplasm then from periplasm to target location - 2 steps
gram -ve only due to 2 membranes
T2 T5 are examples
T2SS
sec-dependent
- 2 step ss
gram -ve
importance for cell physiology and virulence
role in pilus biogenesis
step 1 - proteins moved to periplasm by Sec or TAT machinerry
step 2 - proteins transported across outermsmbrane by T2SS machinery
secretes hydrolyase, toxins
T1SS
one step ss - direct translocation
gram -ve
ABC transporter in inner membrane binds and transports protein across inner membrane using ATP energy
MFP bridgers inner and outer membrane to facilitate transport process
outer membrane secretin - pore-forming protein to secrete protein
this only secretes into the environment
T3SS T4SS T6SS
these are all one step secretions systems that inject into another cell
T3SS
injectisome - molecular syringe
multi-protein machine found in gram -ve bacteria and interacts with animal hosts
function - deliver effector proteins across bacterial membrane into host cytoplasm
mostly gram -ve but some +Ve
T3SS structure
translocon - tip in host cell membrane that has puncture membrane and allows proteins to pass through host membrane into cytoplasm
needle complex - spans bacterial membrane to host cell membrane, piercing host cell membrane - hollow flexible
basal body - membrane anchored base supports secretion machinery
T4SS
DNA and protein transfer - target cells like animal and bacteria
found in +Ve and -ve - role in pathogenesis
used for protein secretion, horizontal gene transfer (conjugation)
T6SS
gram -ve bacteria, role in inter bacterial competition, virulence and host-pathogen interactions
weapon like -crossbow , dynamic firing
mostly gram -ve
example function of T1SS
toxic secretion - like hemolysin into extracellular space, to attack host cells or virluence
enzyme secretion - like lipase or protease to aid in nutrient acquisition or tissue degradation
example functions in T2SS
protein secretion - secreting folder proteins, virulence factors or digestive enzymes to break down host tissues
biofilm formation - secrete adhesions to adhere to surfaces
example functions in T3SS
pathogenesis - injecting effort proteins into eukaryotic host cells, mainuplate host cell processes and infect or immune evade
virulence - to induce cell death and disrupt host defence mechanisms
example functions in T4SS
DNA transfer - conjugation, into other bacteria, spread antibiotic resistance, spread DNA or plasmids
effector secretion - secrete proteins into eukaryotic cells
inter bacterial competition - secret toxins into competing bacteria for intraspecific competition
example functions in T6SS
inter bacterial competition - injecting toxin proteins into bacteria to kill
pathogenesis - inject effector proteins into human cells to kill
biofilm formation - bacteria to target competitors in biofilm environment
