Class Notes (808,858)
Canada (493,417)
York University (33,539)
Biology (2,145)
BIOL 2021 (188)

Ch. 16 - Cytoskeleton - Part 2 A summary of chapter 16 and lecture notes on the cytoskeleton. Includes illustrations and graphics from the textbook.

14 Pages
Unlock Document

York University
BIOL 2021
Julie Clark

th BIOL 2021- April 288 2009 CHAPTER 16 PART 2: MOTOR PROTEINS AND CELL MOVEMENT MOTOR PROTEINS - Myosin: motor head and selective head - Myosin II:  Two heavy chains and 2 light chains  Tail= coiled coil  Found in muscles -> muscle thick fibers  Heads facing in opposite directions KINESIN - Same family as myosin - Moves on microtubules - 2 heavy chains and 2 light chains - Motor domain and coiled coil tail - On microtubules and walk to the plus end (most do)  A few go to the minus end - Tail has a binding site that attaches;  Binds to an organelle or microtubules - Function: carry organelles OR slide microtubules DYNEIN - Moves on microtubules - All go to minus end - Variable numbers of chains - Found in vesicle trafficking and in cilia and flagella Q- no known proteins move on intermediate filaments because of no polarity MOTOR PROTEIN MECHANISMS - All involve ATP binding and hydrolysis causing motor proteins to undergo large conformational changes and changes in the affinity for the filament Mechanical cycle 1) Filament binds to motor head 2) Can’t change in motor protein 3) Releases from filament 4) Large conformational change is reversed-> relaxation of conformation 5) Filament rebinding MYOSIN CYCLE 1) No ATP; heads tightly attached to actin (1 head is useless) 2) ATP binding, causes conformational change which releases from actin 3) Conformational change; ATP hydrolysis  Lever arm moves (big conformational change) 4) Binds back to actin; phosphate release; power stroke (when it pushes against actin) 5) ADP leaves causing tight binding to actin KINESIN CYCLE - Two heads work together 1) Front head loses ADP and binds ATP causing tight binding to tubules 2) Causes conformational change in Linker region: - Rear head forward - Linker region - Loose binding to tubulin 3) ATP hydrolysis and release of rear head DYNENIN - Don’t know much about it so who cares Examples of how cytoskeleton and motor proteins work together - Organelle transport: motor proteins are carrying organelles - Plus end directed kinesins - ER carried outward on motor proteins (ER location below) - Minus end directed dynein carries Golgi inward (below, fluorescence and phase contrast) - Myosin and actin can also move organelles - How do organelles know which way to go? MUSCLE CONTRACTION - Skeletal muscle cells (above) - Muscles depend on movement of actin and myosin SKELETAL MUSCLE  Muscle fiber: giant multinucleated cell  From fusion of myoblasts  Within the cell are many myofibrils; chain of contractile units  Fig 16-74a Transmission electron micrograph of myofibrils - Many myofibrils in parallel - One unit is a sarcomere - In sarcomere: actin thin filaments and myosin thick filament - Actin attached to 2 disks - Contraction is a slide of myosin against actin (actin + myosin do not get shorter; distance between Z disks gets shorter)
More Less

Related notes for BIOL 2021

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.