Lecture 9 Flashcards
intermediate filaments
provides mechanical strength and help cell resist shear stress
- keratin
- neuro filaments. helps hold axons in neurons
microtubules
aid in positioning of internal organelles and intracellular transport
actin filaments
help in shaping the cell and in whole cell locomotion
microtubules and actin filaments
are very dynamic. constantly changing.
sarcomere
from one z disk to another
making filaments
- Made of small protein subunits
- Subunits are held together by weak non-covalent interactions
- Accessory proteins interact with filaments to allow for highly organized internal structures
filaments made as protofilaments
- May be multiple long strings of subunits joined end to end and associate laterally
- Twist around one another - makes them really stable and strong
of protofilaments
actin
microtubules
intermediate filaments
2
13
4
Stability also depends on the subunits
Actin
Intermediate filaments
- has small globular subunits
- have longer subunits making them a little stronger
polar vs non polar filaments
- not about interactions w aqueous envir
- polar (different ends) and non polar (same ends)
for the polar ends they call them + and - ends
- they are not charge
- things are going to be added added/subtracted faster on plus end
- minus end can add but slower
microtubules - polar
- alpha tubulin and beta tubulin
- form dimers to make protofilament
alpha tubulin and beta tubulin bind to
GTP (just changes shape). alpha tubulin doesnt hydrolyze, but beta tubulin hydrolyzes GDP and has different shape.
Multiple versions of the same protein
isoforms
centrosome (or MTOC)
is not an organelle bc it has no nucleus. non membrane bound
nocodazole
drug that inhibits formation of microtubule filaments. binds subunits and prevents polymerization
antibodies
highly specific proteins. They have shape of a Y. has disulfide bonds (formed by cysteine). They are tertiary structure. Antibodies stick on one end, on flurescent.
actin filaments are what?
- polar
- globular monomer called g-actin
- g actin binds ATP
where are the plus ends?
on the outer part of microtubule
where are plus and minus ends on actin?
they are not organized. theyre everywhere.
centrifugal
going out. toward periphery
centripetal
going in. toward center
cortical actin
outer portion. allows for cell movement.
actin part 2
ropelike structures that provide strength and flexibility. important for motility and structure; highly dynamic structures
intermediate filaments part 2
- not polar
- not required in all cell types
- coiled coil proteins
- for structure
- dont change
- 2 monomers are parallel to each other in dimers
- 2 dimers link together antiparallel to make tetramer (staggered)
tetramer is considered what?
protofilament- both ends look same
-need 8 parallel protofilaments to pack together 8x4=32 (strength) to make filament
what is protofilament?
string of g actins that are bound together
Type of intermediate filaments
axonal
neurons
-neurofilament proteins (help in organization)