Final: Ch 18 Kinesins and Dyneins Flashcards
motor proteins (kinesins and dyneins) move along _________ powered by ____ hydrolysis
microtubules, ATP hydrolysis
2 main families of motor proteins that move cargo along microtubules
kinesins
dyneins
organelles in _____ are transported along microtubules in both directions
axons
a neuron has to supply new materials to the axon terminals
microtubules are oriented with which end toward the axon terminal?
+ end
axonal transport occurs in which direction?
cell body toward the axon
used chase-pulse
inject radioactive precursors and see where they end up
anterograde transport occurs in which direction in neurons
cell body to synaptic terminals
associated with axonal growth and delivery of synaptic vesicles
retrograde transport occurs in which direction in neurons
synaptic terminals toward the cell body along the axon
transportation of old membrane from the terminals (degraded by lysosomes)
what did experiments with the squid giant axon reveal?
movement of vesicles along individual microtubules requires ATP
movement can move in both anterograde and retrograde directions
speed is similar to fast axonal transport in intact cells
neurofilament movement is different why?
they pause frequently as they move down the axon
used GFP
______-1 powers ________ transport of vesicles down axons toward the __ end of microtubules
kinesin-1, anterograde, + end
squid giant axon kinesin-1 structure
2 head domains connected by a short flexible linker domain to a long stalk
2 small tail domains
function of kinesin head domains
binds microtubules and ATP
responsible for the motor activity
function of kinesin linker domain
forward motility
function of kinesin stalk domain
dimerization
function of kinesin tail domain
binding receptors on the membranes of cargo
assay to track kinesin vesicle movement
vesicle or bead coated w/ kinesin-1 is added to a glass slide + microtubules
adding ATP causes movement down the microtubule in 1 direction (- to + end)
kinesin-1 is called a __ end-directed microtubule motor protein and transports in the _________ direction
+ end, anterograde
what kinds of functions do kinesins perform
organelle, mRNA and chromosome transport
microtubule sliding
microtubule depolymerization
what techniques were used to find out how kinesin moves down the microtubule
optical traps
fluorescent-labeling techniques
is kinesin-1 a highly processive motor?
yes
takes hundreds of steps by walking hand over hand down a microtubule without dissociating
kinesin stepping cycle
leading head binds ATP, which induces a conformational change
linker docks into the head, propelling the trailing head forward
new leading head (former trailing head) binds weakly to the microtubule and releases ADP, causing tight binding
trailing head hydrolyzes ATP –> ADP + Pi and binds weakly
dynein motors transport _______ toward the __ end of microtubules
organelles, - end (retrograde)
structure of dynein
2 large, 2 intermediate, 2 small subunits
domains of dynein
2 heads
a stem
linker
what part of dynein contains the AAA ATPase domain?
where is the stalk?
the head
btw 4th and 5th AAA subunits, contains microtubule binding region
can cytoplasmic dynein mediate cargo transport by itself?
no, it requires the dynactin protein to link dynein to its cargo
dynactin 2 domains
one domain of actin-related protein Arp1 – binds cargo
CapZ caps + end
2nd domain of p150^glued – dynein binding site + microtubule binding site
what holds the 2 dynactin domains together
a protein called dynamitin
when overexpressed, blows apart the 2 domains
2 major functions of dynactin
bind cargo
make dynein more processive
regulation of dynein
dynactin p150^glued binds +TIP EB1 so the dynein is associated with the growing + end of microtubules
this form is inactive until it reaches the cell cortex where an activator activates it
kinesins and dyneins cooperate in the transport of ______ throughout the cell
organelles
orientation of microtubules is fixed by the ______, so direction of organelle transport depends on the ____ ______
MTOC, motor protein
the golgi apparatus collects where
near the centrosome where the - ends of microtubules are
driven there by dynein-dynactin
secretory cargo from the ER is transported to the golgi by what
dynein-dynactin (b/c - end is near the golgi)
the ER is spread throughout the cytoplasm by what
kinesin-1 b/c + ends of microtubules are located at the periphery of the cell
organelles of the endocytic pathway are associated with which motor protein
dynein-dynactin
ex. late endosomes, lysosomes
what happens when kinesin reaches the end of the microtubule
carried back (retrograde) on organelles transported by dynein
______ modifications distinguish different microtubules and their accessibility to motors
tubulin
the stability and functions of different classes of microtubules are influenced by what
post-translational modifications
ex. acetylation of lysine in alpha-tubulin are stable, detyrosylation also increases stability
kinesin-1 interacts preferentially with which types of modified tubulin
acetylated and detyrosylated microtubules
__________ has a key role in the beating of cilia and flagella
polyglutamylation
does kinesin do exocytosis or endocytosis?
exocytosis
does dynein do exocytosis or endocytosis?
endocytosis
are the +, or - ends of microtubules located at the periphery of a cell?
+ ends near periphery
- ends near nucleus
is dynein in cilia and flagella?
yes, causes movement of sperm/cilia of lungs
moves damaged stuff back to cell for degradation
kinesin-5
form bipolar motors that cross link antiparallel microtubules
by walking toward + ends of each microtubule, causes sliding
kinesin-14
moves toward - end
mitosis
