Lec 34 Guest Flashcards
What is the tol pal system important for
What is it made of and what actually happens
Bacterial cell envelope integrity and function
TOL Q R A B and Pal
They facilitate the transfer of energy from the inert membrane to the outer membrane on gram negative bacteria
What does the tol Q and Tol R in the tol pal system use
The proton motive force
Which is the energy needed to move protons through the membrane
What is the limiting factor in a SPA (single particle analysis)
The high quality data is limited by The sample of purified protien
What is the cryo em show of tol Q
Showed that tol Q had five chains as a pentamer
Each chain sits perpendicular to the inner membrane
Each chain had seven aplha helices with 2 5 6 and 7 forming an extended helix separated by a kink (meaning the helix was not continuous because there’s a kink in it)
Using the MOLE software, what did they find out about tolQ
It forms a transmembrane channel with a cytoplasmic cavity at the inner membrane
This channel has a big cytoplasmic cavity with five vent like things that allow solvent or ion passage
This is cytoplasmic chamber is negatively charged
What shows that the transmembrane region of the channel is very important
Most point mutations that are fatal to its function are located inside the transmembrane channel
Also there are highly conserved residues in that transmembrane channel
What did we learn about the tol Q Chanel and how
Through AF2 modeling and cryo EM
Learned that the pentameric TolQ transmembrane channel actually has 2 TOLR helices within it
Also the disordered N terminal domain of tol R was positively charged and held inside the negatively charged cytoplasmic chamber of TOLQ
When comparing the app tolQ to tol Q with tol R what was found
The structure of tol Q changed in the periplasmic site
The pore went from round (apo) to oval (when tolR)
What did they find about the transmembrane helices of TOLR in the TOLQ structure
They found the the two aplha helices chains related to each other teanslationally meaning that moving one in the x y x direction they still looked the same as each other
What is special about the translational and rotational movement of the TolR
In TOLR there is a D27 residue which they thought functions as a proton binding site
These aspartame residues were translationally related to each other
This is different to the homologous aspartate residues which have rotatiaonal movement
Had to take into account the rotational and translational movement
What did they find about the TOLQ TOLR complex using MDS (molecular dynamics simulations)
And what did they conclude
There’s no continual movement of potassium ions across the tolQ channel when tolR is there, ions aren’t permitted inside the channel
So a conformational change to the non permeable conformational state occur when tolR present
What did modeling the tolQ tolR complex with tolA show
The tol A has a transmembrane helix whiz is oreintated at an ABC angle with respect to tol Q
Making it so the periplasmic part of tolA is inserted into the c terminal periplasmic domain of the TOLR
And interacted with periplasmic part of tolR by forming parallel beta strands
How does the tolQ TOLR and tol A work together
So tolR Inserted into tolQ
But needs tolA for activation
Then assymetric tol a interacting in perimolasmoc domain with tolR to allow serial rotation of the tol Q channel
After full rotation of tol Q tolA a pulls in tol B away from pal which causes dissociation of pal
