Lesson 21: Cytoskeleton 4: Actin Motors and Regulators

light

Calmodulin (CaM) = myosin _______ chain - binds and stabilizes neck region

yes

did u look at it

bi

Non-muscle myosin II regulated by phosphorylation, forming ___polar filaments

-organizes actin cytoskeleton, roles in adhesion, cell migration, etc.

VI

Myosin ___ is the opposite and is MINUS end directed!

X

Myosin ___ moves cargo to the tips of filopodia

III, XV, VI

Myosin ___ and ___ transport cargo to the tips of stereocilia, Myosin ___ moves cargo OUT of stereocilia

size, directionality

myosin power stroke dictates step ____ and _________

II, thick

Muscle myosin is myosin ___ AKA ____ filaments

M, Z

myo II thick filaments are anchored at the __-line

thin filaments have plus ends anchored at the __-disc

ATP

the rigor state happens when no more ____ is generated

rigor

Myosin II/muscle mechanochemical cycle:

1. Attached (nothing bound, attached to actin filament in ______ configuration)

2. Released (molecule of ATP binds, lets go of actin filament)

3. Cocked (hydrolysis moves it back a bit)

4. Rebinding/Power Stroke (weak binding and ADP/P leave, causing large movement forward)

5. back to step 1

Calcium

What molecular signal triggers activation of actomyosin contraction?

acetylcholine

Striated Muscle contraction:

1. neuron releases __________

2. electrical impulse propagates through T-tubules

3. triggers saarcoplasmic release of Ca into sarcomeres

4. calcium binds to troponin so tropomyosin unblocks site on F-actin for myosin motor domain to bind and move

5. calcium pumps push Ca back into the sarcoplasmic reticulum

phosphatase

Smooth Muscle contraction:

1. calcium-bound CaM activates myosin light chain kinase

2. phosphorylates myosin light chain

3. activates myosin motor

4. causes contraction

5. TURNED OFF BY A ______