Dr. Seidler's Lectures on Contractile fibers

Question 1

Myosin is composed of

Answer 1

coiled coil of two alpha helices:
2 heavy chains and 4 light chains

N terminus, hinge region, and a minus end

Question 2

bipolarity

Answer 2

N terminus/hinge region—-minus end

Question 3

what pars of the myosin coiled coil’s associate?

Answer 3

the minus ends to form the bare zone

Question 4

There are ____ heads, ____ chains, and one ____ domain in myosin

Answer 4

2 N terminus heads (globular)
2 heavy chains, 4 light chains
rod domain (helical)

Question 5

Where does myosin self-assembly?

Answer 5

at the tails

Question 6

Muscle tissue is “in register”: what does that mean?

Answer 6

the striations line up together to form larger striations

Question 7

how many thin filaments surround a thick filament

Answer 7

6

Question 8

what anchors the thin filament?

Answer 8

the Z disc, “anchored” to Z disc

Question 9

There is a ____ degree of rotational symmetry of the thin filament around the thick filament

Answer 9

60 degrees

Question 10

what gives the thick filaments the ability to stack AND move around?

Answer 10

the linker protein

Question 11

myosin has _____ amino acids per turn

Answer 11

3.5

so there are 7 amino acids per 360 degrees?
7

Question 12

What kind of amino acid would we expect to find in the interior of the myosin?

Answer 12

hydrophobic

Question 13

rigor mortis

Answer 13

respiration doesnt occur, so oxidative phosphorylation isn’t occurring, so the thin filaments aren’t being dragged along by the head groups (the myosin needs the ATP): the myosin remains attached (does not dissociate)

Question 14

what kind of disease leads to a point mutation in the code for myosin?

Answer 14

a dominant

Question 15

how many possibe binding partners does an actin (thin) filament have?

Answer 15

4

Question 16

Tropomodulin

Answer 16

caps the minus end of the thin filament (not the Z disc)

Question 17

CapZ

Answer 17

b-actinin, a heterodimner which associates with a-actinin, caps at the plus end

Question 18

Troponin complex

Answer 18

Troponin T, I, C

Question 19

Troponin T

Answer 19

binds tropomyosin and positions the complex on the filament

Question 20

Troponin I

Answer 20

binds actin, inhibits myosin binding

Question 21

Troponin C

Answer 21

binds Ca, relieves inhibition

Question 22

Tn-I

Answer 22

inhibitory troponin: has three isoforms found in tissues.

cTn-I is found in cardiac tissue and its serum levels rise after a myocardial infacrtion

Question 23

cTn-I

Answer 23

the isoform of inhibitory troponin that appears in serum after an infarction

Question 24

what method helps distinguish a myocardial infarction in the lab

Answer 24

an ELISA looking for cTn-I

Question 25

TIC

Answer 25

three small troponin proteins that transduce the role of calcium in muscle contraction

Question 26

what initiations contraction? ATP or Calcium?

Answer 26

Calcium

Question 27

What troponin does calcium bind to?

Answer 27

troponin C

Question 28

What actin monomer is in the assembled state?

Answer 28

G actin

Question 29

What actin monomer is in the depolymerized state?

Answer 29

F actin

Question 30

Pointed End

Answer 30

the end fixed to the Z disc

Question 31

the barbed end

Answer 31

hanging in space

Question 32

what are the proteins that make up the thin filaments?

Answer 32

actin, tropomysoin, regular intervals of the troponin complex

Question 33

alpha-actinin =

Answer 33

make up proteins that arrange the actin monomers in the hexagonal arrangement these are within the actin bundles of myofibrils

Question 34

actins are held together at the Z discs by

Answer 34

alpha actinin

Question 35

the myofibrils are held together by

Answer 35

desmin

Question 36

Returning to the question of the myofibrils held in register, what does this?

Answer 36

the Z discs are all aligned two ways: a) the a-actinin anchors the actin at the designated point (the Z disc); these areas are then linked together by DESMIN these then tether to costameres: these are tethering proteins to the sarcolemma

Question 37

costamere protein

Answer 37

dystrophen, tethers the myofibrils to the sarcolemma

Question 38

Titan

Answer 38

Sarcomere ruler "molecular ruler" BALANCES forces across the sarcomere. passive elasticity muscle signaling allows for elasticity without ripping

Question 39

DHP channel

Answer 39

it's responsive to the action potential, but it's mechanically DHP is voltage dependent that is mechanically gated: it opens (mechanically) the ryanodine receptor.

Question 40

Hypocalcemic does what?

Answer 40

releases inhibition of the sodium channel and causes it to spontaneously fire results in tetany

Question 41

Myosin light chain kinases

Answer 41

smooth muscle lacks troponin complexes, so these proteins are activated by calmodulin (Ca activated): MLCK then phosphorylated myosin light chain, enabling a myosin crossbridge to bind to the actin filament and permit contraction

Question 42

Calmodulin-MLCK

Answer 42

the main pathway for smooth muscle contraction

Question 43

Duchenne muscular dystrophy

Answer 43

X linked, reessive disorder with an incidence of 1/3500 boys progressive muscle wasting result from mutations in dystrophen gene (costamere)

Question 44

GSD V/McArdle disease

Answer 44

deficiency in muscle glycogen phosphorylase autosomal recessive disease deficiency in glycogen phosphorylase, rate limiting enzyme of glycogen degradation cleaves glucose residues from glycogen for release as glucose-1 phosphate. marked by myoglobin in the urine during intense exercise individuals suffer immense fatigue because they can't get glucose

Question 45

GSD VI

Answer 45

mutations in chromosomes 14/11 cause mutations of phosphorylase = Hers Disease in the liver

Question 46

GSD V versus GSD VI

Answer 46

GSD VI occurs in the liver. GSD V is activated by AMP, Ca-Calmod, and G actin. GSD VI is inactivated by glucose and no affected by AMP both forms are activated by phosphorylation catalyzed by PhK

Question 47

Duchene

Answer 47

no dystrophin

Question 48

Beckers

Answer 48

truncated dystrophin

Question 49

what does dystrophin do?

Answer 49

tether's outer bundles of myofibrils to surface membrane

Question 50

dystrophen is in the

Answer 50

carsomeres: helps withstand strenuous exercise

Question 51

what happens if you didn't have dystrophin?

Answer 51

your muscles would rip

Question 52

What mediates the glycogen to glucose degradation in the liver?

Answer 52

glycogen phosphorylase

Question 53

What mediates glucose-6-phosphate breakdown to pyruvate in the liver?

Answer 53

Glucose-6-Phosphatase

Question 54

Glycogen Phosphorylase is activated by

Answer 54

AMP signaling

Question 55

AMP binds to what site on Glycogen phosphorylase?

Answer 55

the "s" catalytic subunit (it's the allosteric, not active site)

Question 56

How is glycogen phosphorylase activated?

Answer 56

AMP bings to an allosteric site and a phosphorylase P's a serine residue, increasing its activity

Question 57

phosphorylase kinase

Answer 57

activated by calmodulin, it then activates glycogen phosphorylase