Motor Protein Kinesin

Motor Protein Kinesin, what are they made of

dimer with two identical motor heads

each head consists of catalytic core and neck linker

kinesin structure

Motor Protein Kinesin, what do they do

pull organelles along microtubule tracks

organelle attaches to other end (opposite motor heads) of long coiled coil tether

kinesin heads

contain tightly bound ADP

move randomly

driven by brownian motion

kinesin heads process

1. ADP bound

2. when one kinesin head encounters microtubule, binds tightly to it → ADP released from attached head

3. ATP rapidly enters empty nucleotide binding site → neck linker zippers onto catalytic core → second head thrown forward

4. second head thrown near next binding site on microtubule

5. trailing head hydrolyzes ATP, releases phosphate

6. neck-linker unzippers from trailing head

7. leading head binds ATP, zippers neck linker onto catalytic core, cycle repeats

kinesin heads process part 1

1. ADP bound

2. when one kinesin head encounters microtubule, binds tightly to it → ADP released from attached head

3. ATP rapidly enters empty nucleotide binding site → neck linker zippers onto catalytic core → second head thrown forward

kinesin heads process part 2

1. second head thrown near next binding site on microtubule (releases ADP?)

2. trailing head hydrolyzes ATP, releases phosphate

3. neck-linker unzippers from trailing head

4. leading head binds ATP, zippers neck linker onto catalytic core, cycle repeats

zipping action

neck linker unzips by binding of ADP

neck linker zips by binding of ATP

zipper order

first head that binds zips first

one head thrown forward

first head = trailing head unzips

head thrown forward zips