Kinesins and Dyenins Flashcards
Where are kinesins found?
Almost all eukaryotic cells
Kinesin 1 structure
Tetramer- 2 heavy/light chains. Head binds to microtubule, neck, stalk, tail binds to cargo to be hauled.
How do kinesins walk?`
1 head binds to microtubule, causes conformational changes in the adjacent neck region of the motor proteinthat make other head move forward toward the next binding site on the protofilament.
Where do kinesins walk?
+ end
What moves cilia and flagellas?
Dynein
Dynein structure
Globular head, stalk
Where do dyneins walk?
along microtubule to - end
What do dyneins do?
Position mitotic spindle, move chromosomes, position organelles, vesicles, particles through cytoplasm
How do cilia move?
Oar, coordinated
How many flagella does a cell have?
1 or 2
Cilium structure
Core made of 9 microtubule array surrounding pair of microtubules, + ends at tip of projection.
Nexin link
Complex with proteins regulating dynein activity
What is at the base of cilia? What is a cilia’s structure similar to?
Basal body, centriole
Primary vs 2ndary cilia
Cilia that was already there vs new cilia
What is the mechanism of cilia movement?
IFT proteins line up, brought to cell body by dynein complex. sliding adjacent microtubular doublets relative to one another.
In step 1 of Figure 9.33, the dynein arms anchored along the A tubule of the lower doublet attach to the binding sites on the B tubule of the upper doublet. In step 2, the dynein molecules undergo a conformational change, or power stroke, that causes the lower doublet to slide toward the basal end of the upper doublet. This conformational change in a dynein heavy chain is depicted in Figure 9.32b-e. In step 3 of Figure 9.33, the dynein arms have detached from the B tubule of the upper doublet. In step 4, the arms have reattached to the upper doublet so that another cycle can begin. (An electron micrograph of an axoneme showing the dynein arms from one doublet attached to the adjacent doublet is shown in Figure 18.21.
What forms adjacent doublets in cilia?
Nexin link
What motors operate with actin filaments?
Myosin
Which direction do myosins move?
Barbed end
myosin structure
Motor (head) domain with actin filament and site that binds/hydrolyzes ATP, tail
What are conventional myosins used for?
Mainly muscle contraction, but also splitting cells in 2 during cell division, tension at focal adhesions, cell migration, turning behavior of growth cones
Myosin 2 (conventional) structure
f (1) a pair of globular heads that contain the catalytic site of the molecule; (2) a pair of necks, each consisting of a single, uninterrupted α-helix and two associated light chains; and (3) a single, long, rod-shaped tail formed by the intertwining of long α-helical sections of the two heavy chains.
Are myosin 2 molecules permanent?
No
Myosin one (unconventional)
Exerts tension on membrane, one head, can’t assemble into filaments in vitro
How does myosin one unconventional work?
Both heads attach to underlying filament, head detaches moving forward, other head does the same
ADD STUFF FOR MYOSIN V, IT WAS ON THERE BUT YOU GOT TIRED
