Motor Proteins (associated with actin filaments) Flashcards Preview

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Flashcards in Motor Proteins (associated with actin filaments) Deck (88):
1

makes muscles contract

myosin II

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structure in skeletal muscle made of multiculeated cells

fibers

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each cell from fibers contain a bundle of:

myofibrils

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each myofibril contains thousands of contractile units called:

sarcomeres

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links ECM to cytoskeleton in muscle cells

dystrophin glycoprotein complex

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signaling molecule in skeletal muscle

NOS

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muscle contraction increases levels of:

Ca2+

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Ca2+ increase during muscle contraction activates:

NOS

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activation of NOS in skeletal muscle produces:

NO

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caused by NO diffusion to blood vessels

smooth muscle relaxation

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relaxing smooth muscle causes increased:

blood flow to muscle tissue

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label the parts of a sarcomere

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thin actin filament charge type embedded in Z-disk

positive charge

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consists of thin filaments

I-band

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consists of bipolar myosin thick filaments

A-band

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first molecular motor identified from skeletal muscle

Myosin II

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this part located at myosin N-terminus

globular heads

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myosin globular heads at N-terminus contain:

force generating machinery

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myosin globular heads, light chains, and hinge region connected to:

coiled-coil of two alpha helices

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approach to ID functional domains within a protein is to:

cleave into fragments site-specific proteases

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cleaves myosin into two fragments (heavy- and light-mero-myosin)

Chymotrypsin

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protease cleaves HMM (heavy-mero-myosin) into subfragment 1 (S1) and subfragment 2 (S2)

Papain

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subfragment contains myosin head and neck regions

S1

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these comprise the myosin tail

S2 and LMM

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intrinsic ATPase activity resides in this myosin fragment

S1

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actin binding ability resides in this myosin fragment

S1

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S1 ATPase activity enhanced/activated by:

F-actin

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these wrap around neck region and make it more rigid

light chains

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type of skeletal muscle fibril can be immobilized on glass slide

myosin

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end of actin that myosin "walks" to

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+ end

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actin is moved in direction of this charge on it

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- end

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using actin movement assay, these parts of myosin can move actin

HMM and S1

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myosin domain determines cargo specificity

tail domain

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part of myosin responsible for speed of actin filament movement

myosin neck

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number of S1 myosin domains encoded in human genome

40 domains

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these myosin families are widely distributed among eukaryotes

Myosin I, II, and V

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all membrane associated actin filaments have this end pointed toward the plasma membrane

+ end

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myosin class is the only with a single head

class I

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myosin class binds specific receptors on organelles

Myosin V

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myosin class involved in organelle transport

Myosin V

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myosin class involved in membrane association and endocytosis

Class I

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type of myosin is unique because it forms bipolar filaments

Myosin II

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Myosin II coiled-coil tails interact with:

tails from other myosin molecules

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part of Myosin II points outward from myosin bundles

myosin head

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Myosin II bundle characteristic/property

bipolar "thick filaments"

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myosin head bound tightly to actin when:

ATP is low

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causes myosin to be released from actin filament

ATP binding

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results in myosin head being in "cocked state"

ATP hydrolysis by myosin

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myosin binding causes it to release this

Pi

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caused by myosin head releasing Pi

"power stroke"

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after power stroke the myosin head remains bound until release of:

ADP

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light exerts this on matter

force

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devise measure very small forces

optical trap

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optical trap uses these three parts

laser beam, microscope, charged bead

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optical trap charged bead attracted to:

intense light at center

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optical trap: force applied to particle depends linearly on:

displacement from trap center

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can be used to measure distance myosin molecules move actin filament each step

optical traps

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optical trap experiment: force can be measured by determining:

how much beam has to be increased to keep filament in place

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myosin type does not continuously interact with actin filaments

Myosin II

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name describing myosin motor that does not continuously interact with actin filaments

non-processive motor

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name describing myosin motor that does not release actin filament

processive motor

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this myosin can make many sequential steps without releasing actin filament

Myyosin V

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describes how long myosin is in contact with filaments for ATPase cycle

duty ratio

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Duty Ratio of Myosin II

10%

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Duty Radio of Myosin V

70%

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myosin type produces optical trap graph produced does not have steps

Myosin II

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myosin type releases ADP at slower rate

Myosin V

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myosin type takes clear 36nm steps, one after another

Myosin V

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each myosin V head moves this far

72 nm

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myosin type moves "hand-over-hand"

myosin V

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actin filament oriented with + end in:

Z disc

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contraction brings myosin thick filament closer to this end of actin

+ end

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actin filaments in sarcomere are stabilized at + end by:

CapZ

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actin filaments in sarcomere are stabilized at - end by:

tropomodulin

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protein extends along thin filament from Z-disc to tropomodulin

Nebulin

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consists of actin binding repeats

Nebulin

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length of Nebulin determines length of:

thin filaments

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large molecule with head in Z-disc and extends to middle of thick filament

Titin

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muscle contraction: action potential at neuromuscular junction travels down:

transverse tubule

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muscle contraction: transverse tubule continuous with:

sarcolemma (PM)

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muscle contraction: action potential triggers:

release of Ca2+

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muscle contraction: Ca2+ released from:

sarcoplasmic reticulum

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muscle contraction: Ca2+ induces change in long molecule strucng head to tail along thin filament

Tropomyosin (TM)

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muscle contraction: protein associated with each Tropomyosin (TM)

Troponin (TN)

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Troponin three subunits

TN-T, TN-I, TN-C

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without Ca2+ this blocks myosin-actin interaction

Tropomyosin

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Ca2+ binds to:

TN-C

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binding Ca2+ to TN-C triggers: 

movement of TM (exposing actin binding sites)

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