Lecture 5: Proteins of Sarcomere and Scaffolding

Question 1

each myofibril is ~ ______ in diameter

Answer 1

~1-2 (mu)m in diameter

Question 2

in a fiber (cell) of 50 (mu)m diameter, there are ~ _____ fibrils

Answer 2

8000 fibrils

Question 3

thin filaments

Answer 3

actin strands and a z-line

Question 4

structural protein in a z-line or disk

Answer 4

alpha actinin

Question 5

where do actin filament attach?

Answer 5

on either side of the z disk

Question 6

alpha actinin converts ___ sided actin filaments to ____ sided structure

Answer 6

alpha actinin converts a 6 sided actin filament to a 4 sided structure (z-disk)

Question 7

globular (G) actin

Answer 7

• globular (G) actin ~ 350/filament

- decrease ATP –> ADP (90% of cells ADP)

Question 8

Filamentous (F) actin

Answer 8

a helix

Question 9

tropomyosin

Answer 9

50/filament covers 7 G-actin

Question 10

Troponin

Answer 10

-50/filament every tropomyosin

Question 11

T

Answer 11

tropomyosin

Question 12

C

Answer 12

Ca++ 4 binding sites

Question 13

I

Answer 13

inhibitory

Question 14

thick filament

Answer 14

myosin

Question 15

myosin heavy chain

Answer 15

~ 300 rods/thick filament

-different isoforms (ATPase)

Question 16

Light chains LC1, LC3

Answer 16

essential

Question 17

Light chain LC2

Answer 17

regulatory

Question 18

myosin head

Answer 18

• 2 heads per myosin molecule
• binding site with actin
• ATP enzyme

Question 19

spacing of heads: the heads rotate at ___ degrees

Answer 19

the heads rotated at 60 degrees

Question 20

why are the myosin heads rotated at 60 degrees?

Answer 20

allows 4 head groups to possibly interact with 1 thin filament?

Question 21

M-line attachments

Answer 21

M-filaments (myomesin)
M4 crosslinks (creatine kinase)

Question 22

titan

Answer 22

• sarcomere support protein
• largest protein in our bodies
• found in both skeletal and cardiac muscle fibers
• tethers the myosin filament within the sarcomere
• acts like a spring
• source of much of the passive elastic force in skeletal muscle
• major mechanism for the Frank-starling mechanism in the heart

Question 23

nebulin

Answer 23

• integral part of actin strands
• acts as a ruler or template to regulate thin filament length during sarcomere assembly
• nebulin-knockout mice

Question 24

nebulin-knockout mice

Answer 24

• die postnatally
• have reduced thin filament length
• postnatal sarcomere disorganization and degeneration
• impaired contractile function

Question 25

cytoskeleton

Answer 25

- anchors myofibrils to eachother - anchors myofibrils to plasmalemma - anchors basement membrane to plasmalemma

Question 26

intermediate filaments of the cytoskeleton

Answer 26

anchor myofibrils to eachother | desmin, vimentin, synemin

Question 27

intermediate filaments of the cytoskeleton desmin, vimentin, synemin

Answer 27

- wrap around z-disk | - keep z disks of adjacent fibrils in register during contraction

Question 28

dystrophin

Answer 28

Duchenne (1861-72') muscle weakness

Question 29

anchoring myofibrils to plasmalemma

Answer 29

cytoskeletal filaments | capping protein, vinculin, talin

Question 30

anchoring basement membrane to plamalemma

Answer 30

transmembrane proteins (integrins), fibronectin receptor, glycoproteins, fibronectin, laminin

Question 31

with an absence of what protein will one die?

Answer 31

dystrophin