Notes taken during lecture

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2 Mar 2011
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LECTURE 14 March 1st
MYOSIN MOTORS microfilaments
To propel along filaments in one direction
Towards plus end
Carry cargo along filaments
Can move filaments along filaments
Myosin II made up of six proteins
Coiled-coil motif of the heavy chain long string with globular domains at the
ends
Light chains regulate activity of globular domains, which are for walking
Acts as a motor because of experiments
oMyosin motors attached to glass slide
oMicrofilaments bound by heads
oAdd ATP and observe movement
oATP-dependent because if no ATP, myosin binds to head but doesnt
move
Biding doesnt require ATP, but movement does
Myosin II motor mechanism
binds actin filament tightly”
Add ATP
Myosin head binds ATP, release microfilament
+ ATP
Conformation change in the head
oLose high affinity for actin
oSo actin filament released
oIs reduced
3. ATP hydrolyses …. Remain tightly bound
5nm to the next monomer down the filament towards the plus end
oStill not bound to filament, but physically moved to plus end
Weak binding.. Pi release
oTriggered by weak interaction between head of myosin and actin filament
oCausing another conformation change, allowing for strong binding motor
and actin
oSo now interaction is strong
oPower stroke ADP pops out
ohooking motion
oBind the filament tightly|
oReturns to its original shape moving the filament
o****POTENTIAL TEST QUESTION ASKING FOR CORRECT ORDER
Thick filament force generating apparatus
Distance between Z disc and Z disc is a sarcomere
oZ discs pulled together this is a muscle contraction
oRelease Z discs spring apart
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Document Summary

Myosin i i made up of six proteins. coiled-coil motif of the heavy chain long string with globular domains at the ends. Light chains regulate activity of globular domains, which are for walking . acts as a motor because of experiments: myosin motors attached to glass slide, microfilaments bound by heads, add atp and observe movement, atp-dependent because if no atp, myosin binds to head but doesn"t move. biding doesn"t require atp, but movement does. conformation change in the head: lose high affinity for actin, so actin filament released, is reduced , atp hydrolyses . 5nm to the next monomer down the filament towards the plus end : still not bound to filament, but physically moved to plus end. distance between z disc and z disc is a sarcomere: z discs pulled together this is a muscle contraction, release z discs spring apart www. notesolution. com. will spring apart completely if not for titin.

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