Cytoskeleton Flashcards
determine the shape of the cell’s surface and are necessary for whole-cell locomotion
form many types of cell-surface projections like lamellipodia and filopodia that cells use to explore territory and move around
actin filaments
determine the positions of membrane-enclosed organelles, direct intracellular transport, and form the mitotic spindle that segregates chromosomes during cell division
form cilia, which function as motile whips or sensory devices on the surface of the cell
can quickly rearrange themselves to form a bipolar mitotic spindle during cell division
Microtubules
What is the monomer of actin filament?
actin
What is the monomer of microtubules?
tubulin
provide mechanical strength
line the inner face of the nuclear envelope, forming a protective cage for the cell’s DNA
intermediate filaments
hold epithelial cell sheets together or help nerve cells to extend long and robust axons, and they allow us to form tough appendages such as hair and fingernails
intermediate filaments
another word for actin subunits
Globular (G) - actin
homolog of tubulin:
which can polymerize into filaments and assemble into a ring; important for cell division and cell fission
FtsZ
homologs of actin:
assemble to form dynamic patches that move circumferentially along the length of the cell; contribute to cell shape by serving as a scaffold to direct the synthesis of the peptidoglycan cell wall
MreB and Mbl
Bacterial homologs of actin:
carry genes responsible for antibiotic resistance and cause the spread of multidrug resistance in epidemics; and ParR proteins important for segregation
ParM
Combination of end-to-end are seen in _____ and ____
actin and microtubule
combination of subunit in side-to-side are seen in ______
intermediate filaments
What type of actin are expressed only in muscle cells?
α-Actin
β- and γ-actins are found together in almost all _____
non- muscle cells
What do you call to the slower-growing end of the actin filament?
minus end or pointed end
What do you call to the faster-growing end of the actin filament?
plus end or barbed end
what do you call to the aggregation of 3 actin subunit to start the elongation?
nucleus
What happens in nucleation process?
actin monomers forming 3 (nucleus)
What happens in actin polymerization process?
elongation of actin filament
What happens in actin treadmilling?
elongation at the same time some loose in the negative end
are fungal products that prevent actin polymerization by binding to the plus end of actin filaments.
Cytochalasins
prevents actin polymerization by binding to actin subunits.
Latrunculin
toxins isolated from the Amanita mushroom that bind tightly all along the side of actin filaments and stabilize them against depolymerization
Phalloidins
prevent the actin filament from interacting with other proteins
important in the control of muscle contraction
Tropomyosin
function in the capping of exceptionally long-lived actin filaments in muscle, binds tightly to the minus ends of actin filaments that have been coated and thereby stabilized by tropomyosin
Tropomodulin
actin-severing proteins (breaks the filament)
are activated by high levels of cytosolic Ca2+
Binds to the side of the filament
Gelsolin
actin-filament destabilizing protein found in Eukaryotes
Cut actin filament
binds along the length of the actin filament, forcing the filament to twist a little more tightly (twisting)
Cofilin (actin depolymerizing factor)
is the motor protein that enables stress fibers and other contractile arrays to contract
Myosin II
Causes the very close packing of actin filaments that exclude myosin
Binds actin filaments together
Fimbrin (straight)
polarized actin filaments into loose bundles, allowing the binding of myosin and formation of contractile actin bundles
Α-actinin (straight)
Organizes a network actin in the brain
promotes the formation of a loose and highly viscous gel by clamping together two actin filaments roughly at right angles
Filamin
Web forming protein
allowing the red blood cell to spring back to its original shape after squeezing through a capillary
important in worms
Spectrin
Protein that ables to move
Myosin II
Composed of actin and myosin
Myofibrils
Largest protein in the human body
Titin
Important for movement within a cell because it moves continuously along the actin filament so parang asa tight rope sya ganern
Myosin V
carry a wide range of cargoes— including mRNA, endoplasmic reticulum, and secretory vesicles
Myosin V
Made of microtubule dimers (alpha and beta tubulin; that are bounded by GTP)
Microtubules
What are the subunit of microtubules?
alpha and beta tubulin
What does plus end of microtubule do?
Exposed here is the B- tubulin
Growing and shrinking
What does the minus end of the microtubule do?
Exposed here is the a- tubulin
What are the 2 types of microtubule?
D form : one with GDP
T form : one with GTP
interact with tubulin subunits and lead to microtubule depolymerization
colchicine and nocodazole
binds to and stabilizes microtubules, causing a net increase in tubulin polymerization
Taxol
Location for microtubules that are nucleated where y- tubulin is most enriched
microtubule-organizing center (MTOC)
The location of the microtubule in animal cell is located in _____
centrosomes
What do you call to the proteins that bind to microtubules?
microtubule-associated proteins, or MAPs.
Type of MAP
determine the organization spaces of the microtubule
long projecting domain, form bundles of stable microtubules that are kept widely spaced
MAP 2
Type of MAP:
shorter projecting domain, form bundles of more closely packed microtubules
Associate with Alzheimer’s disease
Tau
known as catastrophe factors bind to microtubule ends leads to shrinking
Kinesin 13
protects microtubule minus ends from the effects of catastrophe factors
Nezha or Patronin
suppressed catastrophe and keeps growing rather than shrinking
XMAP215
Binds tubulin dimers and prevents their addition to the ends of microtubules
result in shrinking
Stathmin (or Op18)
contribute to the rapid microtubule depolymerization observed at the poles of spindles during mitosis
Katanin
CLASS OF MOTOR :
walking toward the plus end of microtubules
organelles from the axon to nerve terminals
Kinesin-1
CLASS OF MOTOR :
moves towards the negative- end
highly specialized for the rapid and efficient sliding movements of microtubules that drive the beating of cilia and flagella
required continuously for neuronal function
Dynein
allows Dynein to move along microtubule in negative direction in order to transport vesicle within the cell
Dynactin Complex
Where does cilia and flagella structures built from?
microtubules and dynein
Where does myofibrils machine built from?
actin and myosin filaments
What do you call to the bending core of cilia and flagella for their movement?
axoneme
found on sperm and many protozoa
enable the cells to which they are attached to swim through liquid media
Undulating motion
Flagella
Whip-like motion
line our respiratory tract, sweeping layers of mucus, trapped particles of dust, and bacteria up to the mouth where they are swallowed and ultimately eliminated
Cilia
nonmotile counterpart of cilia and flagella
they sense and respond to the exterior environment, functions best understood in the context of smell and sight
Primary cilia
Microtubule-organizing centers (MOC) such as _______ protect the minus ends of microtubules and continually nucleate the formation of new microtubules.
centrosomes
proteins that stabilize microtubules
Microtubule-associated proteins (MAPs)
Counteracting the stabilizing activity of MAPs
“catastrophe factors”
kinesin-13 proteins
moves toward the minus end of microtubules, and its sliding of axonemal microtubules underlies the beating of cilia and flagella.
motor dynein
nonmotile sensory organs found on many cell types
primary cilia
Common structure is the coiled-coil which is a multi-strand rope
intermediate filaments
monomers connect ______ in intermediate filaments
side to side
most diverse intermediate filament family and held together by disulfide bonds
keratins
Bundle of keratin filaments that gives outermost layers of skin
mutation leads to eczema
Filaggrin
second family of intermediate filaments
high concentrations along the axons of vertebrate neurons
Neurofilaments
third family of intermediate filaments
vimentin-like filaments (Desmin)
intermediate filament network is linked to the rest of the cytoskeleton by members of a family of proteins called ______
plakins
links the intermediate filaments to microtubules, actin filament bundles, and filaments of the motor protein myosin II
Plakins (example Plectin)
connects the nuclear and cytoplasmic cytoskeletons
SUN and KASH proteins
proteins bind to the nuclear lamina or chromosomes
SUN
proteins bind directly to actin filaments and indirectly to microtubules and intermediate filaments
KASH
Important to regulate cell polarity
block the movement of proteins from one side of the bud neck to the other, thereby concentrating cell growth preferentially within the bud (mother).
In animal cells, septins function in cell division, migration, and vesicle trafficking
Septin
tissue-specific forms of intermediate filaments in epithelial cells
keratin
tissue-specific forms of intermediate filaments in nerve cells
neurofilaments
tissue-specific forms of intermediate filaments in muscle cells
Desmin
Contain all of the machinery required for cell motility
Lamellipodia
degrade the extracellular matrix, which requires the delivery of vesicles containing matrix-degrading proteases.
Invadopodia
act as molecular switches that cycle between an active GTP-bound state and an inactive GDP-bound state
promotes bundling of actin filaments and clustering of integrins
Rho Protein
promotes actin polymerization at the cell periphery, leading to the formation of sheetlike lamellipodial extensions
Rac Protein
expressed only in blood cells and immune system cells
WASp Protein
movement of a cell toward or away from a source of some diffusible chemical.
Example is neutrophil that moves toward a source of bacterial infection
chemotaxis
