Joint 3 - Moving Cargo Around in the Cell Flashcards
main characteristic of a motor protein?
can convert chemical energy into mechanical energy
- atp hydrolysis coupled with protein shape change
- allow protein to move
two families of motor families?
actinfilament based motor proteins
- MYOSIN is the motor protein [moves along actin filaments]
microtubule based motor proteins
- DYNEINS and KINESINS move along a microtubule
structure of a motor protein: myosin?
Head
- binds to ATP and actin filament
- generates force from ATP
Neck
- links both
- transduces force from head
Tail
- interacts with cargo
structure of myosin II?
- has light chains on head
conclusions about myosin motor proteins?
- head and neck enough to cause movement
- myosin moves along filament towards + end
- a longer neck = faster movement
steps of myosin and actin cross bridge cycle?
- myosin bind to actin
- atp bind to myosin head [conf change]
- unbinds from actin
- atp hydrolyses to ADP + P
- conf change in neck
- movement caused as head is moved along movement
- head binds weakely again to actin
- p released causes power stroke as ADP gets released too
- myosin head back in orig conf
difference between a processive and non processive motor?
processive
- heads independent of each other
- movement un-coordinated attachment of myosi heads
non-pro
- heads are coordinated
- one attaches the other disattacheds
how can myosin II be regulated?
Mysoin Light Chain Kinases/Phosphotatses
- myosin activated when the light chains are phsophorylated
structure of motor proteins: kinesins?
- head and neck and tail
[head binds to microtubule and ATP]
kinesin classes?
cytosillic
- bind to vesicles and organelles
spindles
- spindle assembly
how do kinesins act non-processive motors?
- tubulin dimers have 1 binding site
- lagging head locked to microtubule [bound to ATP]
- leading head [bound to ADP] is weakly bound to MT
- lagging head ATP hydrolyses [ADP/P]
- releases P now makes lagging head weakly bonded
- leading head binds to ATP and locks to MT
- locking causes laggin head to push forward to become leading
- cycle starts again
different locations of motor domain in kinesins?
can be
- at N-terminal end [moves to + end]
- middle
- c-terminal {moves to - end}
- bipolar
2 classes of dynesins?
cytosolic
- movement of vesicles
axonemal
- beating of cilia/flagella
structure of dyneins?
- processive [move to + end]
- doesn’t have a tail so instead proteins on it attach to cargo
- 2 identical heavy chains
how do dyneins move cargo?
- bound to ADP - dynein not bound to microtubule
- atp hydrolysis - dynein stalk attaches
- ADP and P released [conf change caused] causes POWER STROKE as it rotates head
- dyneins are processive
