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35 Cards in this Set
- Front
- Back
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Filament types and sizes
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Actin 6-8nM in diameter, variable length, polarized
Microtubules 20-25nM, variable length, hollow, polarized Intermediate Filaments 8-11nM, not polarized |
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Actin subunits and organization
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G-actin monomers for F-actin polymer spontaneously. ATP on G-actin promotes polymerization
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How is ATP involved in the polymerization and depolymerization of actin?
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ATP promotes the polymerization of G-actin to F-actin. ADP promotes depolymerization when bound to F-actin, so G-actin monomers fall off.
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Why is f-actin polar?
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Polar b/c G-actin monomers are polar and all orient in the same direction, givin + and - ends to the F-actin, actin strand.
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Which end of actin is more commonly used for polymerization and why?
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The + end because g-actin can add to this end faster.
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Disruptors of actin filaments and what they do
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Cytochalasins B & D, prevent polymerization, cells ball up, can't connect, do mitosis
Phalloidin - prevents depolymerization by stabalizing F-actin, cell stretched out, can't do mitosis |
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Duchenne Muscular Dystrophy
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Absense of actin anchoring protein dystrophin or lack of enough dystrophin, which connects actin to plasmalemma of cells, get loss of
stability of whole muscle, when muscle contracts pulls apart plasmamembranes |
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This protein helps with a specific type of cell interaction using actin
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Integrin, anchoring protein, helps with cell to substrate interaction by anchoring actin to substrate
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This is an integral membrane protein, binds actin to extracellular matrix substrates
what is protein and what does that binding help cell to do? |
Integrin, helps cell to attach and move
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What helps regulate actin polymerization/depolymyerization, give an example of a protein of this type
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Binding proteins, myosin
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Some functions/jobs of binding proteins for actin
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Sequester G-actins
Facilitate nucleation step Act as motor protein Bundling protein, creates rows in filopodia Cross-link actin, give cell shape Cap proteins stop polymerization |
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Subunits and assembly of Microtubules
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13 dimeric (alpha and beta) subunits make up tubulin, grow from microtubule organizing center (MTOC)
GTP important for depolymerization |
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Functions of microtubules
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Involved in INTRAcellular motility
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Are Microtubules polar? How are they oriented? Which end do they polymerize on?
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Yes, are polar, regular assembly of heterodimers lends polarity to MTs. Minus end is oriented towards MTOC, Tend to grow at + end, but can grow at both.
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What forms/structures are microtubules a part of?
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Cytoplasmic MTs (alone in cell)
Large order arrays: Centrioles, basal bodies, axonemes, mitotic spindle apparatus |
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What cell structure serves as the MTOC for microtubules?
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centrosome
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What functions/roles (similar to actin)do Microtubules play
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Structural roles (eg disposition of cytoplasmic organelles) and motility events (organelle transport)
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What are MAPs? What function do MAPs have? Give examples of 2 maps and their role.
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Microtubule associated proteins.
Help to organzie MT arrays. Microtubule motor molecules, kinesin (+end directed motor) and dynein (-end directed motor) |
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what does the GTP cap do for Microtubules?
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promotes polymerization
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What does EMS slide of MTOC look like?
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See powerpoint.
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Microtubles grow from what in the MTOC?
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gamma tubulin ring complexes of the centrosome
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what is kinesin and what does it do?
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Motor protein for microtubules, moves stuff from negative center to + ends towards periphery, needs ATP (ATPase)
ANTEROGRADE movement |
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What is dynein and what does it do?
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Motor protein, moves stuff from positive end towards negative ends near MTOC, needs ATP (ATPase)
RETROGRADE movement |
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Are molecular motor proteins specific?
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Yes, different family members of the molecular motors transport specific cargo along microtubules
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What does the MTOC (centrosome) do?
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Controls, in part, the number, orientation, and distribution of microtubules in the cell.
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What two filaments interact for intracellular transport?
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Actin filaments and microtubules
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Disruptors of Microtubules
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Colchicine and Vinblastine- prevent polymerization
Taxol- stabalizes MTs used experimentally and sometimes clinically (cancer treatment) |
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What is primary role of intermediate filaments?
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Structural role, more stable array of cytoskeletal elements than actin or MTs.
Interact with actin and MT highways. |
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Why are intermediate filaments not polar even though have polar subunits?
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Because they have antiparallel assembly of their subunits.
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Desribe structure of intermediate filaments.
What is a major advantage of this structure? |
8 small strands twisted together (antiparallel orientation)
Very strong! Especially resistant to tensile stress. |
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How do classes of intermediate filaments differ?
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In the primary structure of the N and C-terminal domains that connect up to the well conserved rod domain (main piece).
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What are some structural roles of intermediate filaments?
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Anchor and connect cells.
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What are types of intermediate filaments?
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these are families
Keratins (found in epithelia cells) Vimentins (Connective Tissue, mesenchyme) Desmin (in skeletal muscle) Glial Fibrillary Acid Protein (in Glial cells) Neurofilaments (in neurons) Lamins (in nucleus of all cells) involved in nuclear structure |
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Keratins, Vimentins, Desmin, Glial Fibrillary Acid Protein, Neurofilaments, and Lamins are what?
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Types/families of intermediate filaments
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What intermediate filament type is common to all cells and what does it make up a part of?
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Nuclear Lamins, a part of the structural cytoskeleton of the nuclear envelope.
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