Appendages Pili, Sexpilus and Flagella (in E. coli) Flashcards
What are fimbriae/pilli
thin filaments extending a few um from cell. located all over cell surface
What is the structure of pilli
multiple subunits of a protein arrange in helix. subunits held by hydrophobic force and non-covalent bonds. another adhesive protein located at tip
What is the fn of pilli
adhere to surfaces
Where are fimbriae subunits synthesized
synthesized in cytoplasm and exported into periplasm by Sec system
How do fimbriae subunits cross the OM
by using a chaperone usher system. in system subunits bound by periplasmic proteins called chaperones.chaperone deliver subunits to integral OM protein usher complex
What is the purpose of binding fimbriae subunits to chaperones
binding prevents subunits from assembling into fimbriae in periplasm.
What happens to pilli subunits at usher complex
subunits pass through a pore in the usher complex and self assemble into helical fibre that extends from surface of cell
Where does the growth of fimbriae helical fibre start from
from proximal end
What is the structure of the sexpillus
like pilli it is a filament composed of protein subunits. however larger in diameter and longer
What does the F (fertility) plasmid of E. coli encode
the genes for synthesis of sexpillus
What is the fn of sexpilli
used in conjugation to help overcome the electrostatic barrier between cells
When a flagella is peritrichous
multiple flagella all over cell surface. eg E. coli
Name the structural components of flagellum in E. coli
basal body, hook, filament and motor proteins. all made of proteins
Structure of the basal body of flagella
a hollow central rod running through four proteins rings
Describe the four protein rings of the basal body
L ring associated w/LPS. P ring associated w/peptidogylcan. MS ring is in PM, connected to rod. C ring attached to cytoplasmic side of MS ring to indirectly connect to rod
What is the C ring of basal body made up of
multiple copies of 3 Fli proteins
Structure of hook component of flagella
short curved sleeve protruding from cell. connected to the rod of basal body and the filament
Structure of the filament component of flagella
semi-rigid hollow helical filament composed of multiple subunits of a protein called flagellin
What is associated with the MS ring
motor proteins MotA and MotB. MotB anchors MotAB complex to peptidoglycan
Synthesis of the filament
Flagellin synthesized in cytoplasm. transferred to hollow core of the rod and hollow filament. new subunits are added to the distal end
The motor of flagellum
the motor that turns the flagellum is composed of a rotor and a stator
Structure of stator of flagella
stationary, composed of Mot proteins
Fn of stator of motor of flagella
use PMF as source of nrg to turn rotor. proteins pass from periplasm to cytoplasm in channels of Mot proteins. produce a conformational change in Mot proteins, this turns rotor.
Which part of the flagella turns and how
rotor is the C ring. turning of C ring turns the MS ring, the attach rod, hook and the filament. The L and P rings do not turn, they act as bushings
