Motility Flashcards
Taxes
Tactile responses
Flagella general structure
Basal body + hook + filament
Types of flagellum arrangement
Peritrichous and polar
Peritrichous
Multiple flagella arising from along the cell body in a uniform distribution
Lophotrichous
several flagella that are all present at the same place on their surfaces and work together to propel the bacteria in a certain direction
What proteins make up the filament?
Flagellin and FliC
Flagellin
globular protein that arranges itself in a hollow cylinder to form the filament in a bacterial flagellum
Subunit also know as FliC
Rotor
C-ring, MS ring, rod, hook
Stator
MotAB, P and L ring - hold rotor in place
C-ring
Made up of 3 proteins
FliG, M, N
Part of stator complex
FliC
Inside of rod and moves up and assembles on surface of growing filament
How many protons are required for a 360 degree rotation?
300
Switch complex
C-ring
Controls direction of rotation
IMF
Ion motive force
Protonation in MotB
Both protonation and deprotonation of MotB-Asp33 induce conformational changes of the cytoplasmic loop between TM2 and TM3 of MotA (MotAC), which is directly involved in the interaction with FliG
Power stroke
After the initial electrostatic steering, two protons bind to thecharged Asp32 residues on the MotBs. The consequent rearrangement of hydrogen bonds induces an elastic strain in the straight MotA loops. Release of thisstrain results in synchronous kink and swivel motions about the proline hinge in both MotAs. As a result, a steric push is imposed on FliG, and the first half ofthe power stroke is performed by loop 1. Importantly, this motion also has a vertical component—the loops lower themselves out of the membrane. (Bottom)The lowering of the MotA loops exposes the protons in MotB to the cytoplasm, whereupon they are released. This results in a reset of the MotA loops, duringwhich loop 3 carries out the second half of the power stroke. We note that this image depicts a 2D projection of a 3D motion: The motion of the stators is notconstrained to the plane of the page. An observer sitting on the rotor axis sees the stator inchworm walking along the rotor using the FliGs as steppingstones.
CW vs CCW
CheY phosphorylated in CW and unphosphorylated in CCW
CheY interacts w rotor
Smooth swimming
CCW
Flagella bundle together
Straight line
Tumbling
CW
Flagella peritrichous
Random movement + dictates change in direction
Random walk
Switching between CW and CCW
Biased walk
CCW for longer towards attractant
MCP
Methyl accepting chemotaxis protein
