BIO120H1 Lecture : Notes taken during lecture

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redtermite204

2 Mar 2011

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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.

Related Questions

A single myosin head moves an actin filament about 10 nm in a single power stroke, yet the myosin head itself only experiences a 0.5 nm conformational change while attached to the actin filament. How does such a small conformational shift in the myosin head translate into such a large displacement of the actin filament? A) The small head movement is expanded elastically. B) Interaction with the myosin head causes the actin filament to stretch. C) Interaction with the myosin head causes the actin filament to become shorter. D) The small myosin head movement was amplified ~20-fold by the swinging movement of an adjoining, elongated alpha-helical neck that acts like a lever arm. E) The small myosin head movement was amplified about 20-fold by the swinging movement of an adjoining, elongated beta-pleated sheet neck that acts like a lever arm.

raspberrymuskrat393

A.) Microfilaments are composed of globularsubunits of the protein actin. In the presence of ATP actinpolymerizes to form helical filaments. Briefly describe the role ofATP and how necessary for microfilament assembly.

B.) All of the motors known to operate inconjunction with actin filaments are members of the myosinsuperfamily. Name the two major categories of myosin and their maindifferences.

C.) A cell is treated with a fluorescentlylabeled antibody against a specific form of myosin. In thefluorescence microscope, the antibody can be seen immediatelyunderlying the cell membrane and associated with somemembrane-bound organelles. What kind of myosin is it likely to be?Would this cell be able to carry out cytokinesis in the presence ofthese antibodies?

ivoryhornet2

Determine whether each of these statements is true or false and then explain why?

a) Myosin II molecules have two motor domains and a rodlike tail that allows them to assemble into thick filaments with motor domains on either end, which is crucial for the efficient sliding of oppositely oriented actin filaments past each other.

b) When activated by Ca2+ binding, troponin C causes a conformation change in the troponin complex that allows tropomyosin molecules to shift their positions slightly so that the myosin heads can bind to the actin filaments.

c) In most animal cells, minus-end directed microtubule motors deliver their cargo to the periphery of the cell, whereas plus-end directed microtubule motors deliver their cargo to the interior of the cell. (Be sure to name these motors).

d) Both kinesin-1 and myosin II move processively making them suitably adapted for their biological functions.

e) Axonemal dyneins mediate the bending of cilia and eukaryotic flagella.

BIO120H1 Lecture : Notes taken during lecture

BIO120H1 Full Course Notes

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