CSB331H1 Lecture Notes - Lecture 6: Phosphatidylinositol 4,5-Bisphosphate, Brownian Ratchet, Microtubule

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champagnehyena204

4 Apr 2012

School

UTSG

Department

Cell and Systems Biology

Course

CSB331H1

Professor

Maurice Ringuette

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Document Summary

The majority of the notes is verbatim from the 4th and 5th editions of alberts and cited literature. While actin polymerization can push plasma membranes to generate cellular protrusions at the leading edge, movement of cells is also dependent on the interaction of actin cytoskeleton with myosin motors. Myosin motors move along actin filament by hydrolysis of atp to transform chemical energy into mechanical energy- hence myosin motors are often referred to as mechanochemical motors. As noted in alberts, the myosin family is composed of several members. The focused is on myosin i and myosin ii as the play key roles in promoting cellular movements. The tail of myosin i interacts with lipid bilayers, by a still poorly understood mechanism. Via its interactions with the plasma membrane and actin-filaments at the leading edge of migrating cells, it"s hypothesized that myosin i promotes lamellipodia and filopodia extensions.

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

Themicrotubule and actin microfilament cytoskeletons use molecularmotors for transporting cargo (vesicles, organelles) through thecytosol. Speculate on why two families of motors (kinesin anddynein) are associated with microtubule-based transport, while onlyone family of motors (myosin) is associated with actinmicrofilament function has only one. Drawings may be used to helpyour explanation.

brownferret413

CSB331H1 Lecture Notes - Lecture 6: Phosphatidylinositol 4,5-Bisphosphate, Brownian Ratchet, Microtubule

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