Glossary of Cytoskeleton I
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- What is def. of cytoskeleton?
- Complex netwrok of interconnected filaments & tubules extending thruout cytosol, from nucleus to inner surface of plasma mem.
- What are some traits of cytoskeleton?
- Architectural framework for the cytoplasm
Dynamic and changeable
Critical for many cellular processes
- What are components of cytoskeleton?
- Describe microfilaments.
- Actin protein
7 nm diameter
- Describe intermediate filaments.
- Different proteins
depending on cell type
8-12 nm diameter
- What are accessory proteins?
- For all cytoskeletal elements
Give wide structural and functional diversity
to the cytoskeleton
- What are techniques for studying cytoskeleton structure?
- -Immunofluorescent microscopy
-Computer enhanced digital videomicroscopy
-Fluorescence techniques for living cells
- What are techniques for studying cytoskeleton function?
Drugs that disrupt specific cytoskeletal
Mutations in cytoskeletal proteins using a
molecular genetic approach
- What are the 2 anti-cytoskeletal drugs?
- Anti-microtubule drugs
- What are the anti-microtubule drugs and how do they work?
-Alkaloid from the Autumn crocus, Colchicum autumnale
-Binds to tubulin monomers
-Prevents formation of microtubules
-From the Pacific Yew, Taxus brevifolis
-Binds to microtubules
- What are the anti-actin drugs and how do they work?
- Cytochalasin D
-Red Sea sponge Latrunculia magnifica
-Both inhibit polymerization of actin monomers into
-Toxin from Amanita phalloides
-Blocks depolymerization of microfilaments
- What are microtubules?
- Largest cytoskeletal elements
Straight, hollow cylinders
15 nm inside diameter
25 nm outside diameter
- What are the 2 types of microtubules?
- Two types
Differ in degree of organization and structural
- What are traits of axonemal microtubules?
- Highly organized
Found in specific
Cilia, flagella and
- What are traits of cytoplasmic microtubules?
- Loosely organized
Observed initially by
now more commonly
- What are functions of cytoplasmic microtubules?
- Various functions
including maintenance of:
Mitotic and meiotic
Spatial distribution and
directional movement of
vesicles and organelles
- Describe the microtubule structure.
- MT wall composed
of longitudinal arrays
of linear polymers or
- What is tubulin?
- The protein that
Basic subunit of a
protofilament is a
heterodimer of α-
tubulin and β-tubulin
- Describe the alpha/beta-tubulin molecules.
- 4-5 nm diameter
40% amino acid sequence identity
Almost identical 3-dimensional structure
GTP-binding domain at N-terminus
Middle domain (colchicine binding)
MT-associated protein (MAP) domain at C-terminus
- What are tubulin isoforms?
- Different forms of α-tubulin and β-tubulin
Differ in the C-terminal, MAP-binding domain
- How does microtubule polymerizatoin occur & what is required?
- Formation by reversible polymerization of
In vitro formation requires tubulin dimers,
GTP, and Mg2+ warmed from 0oC to 37oC
- What are steps in microtubule polymerization?
- Dimers → oligomers (nucleation) →
protofilaments→ sheets of protofilaments →
closing microtubule → elongating microtubule
- What are the terms/steps associated with the formation of microtubules?
- Slow start or lag phase
Active growth of MTs is the elongation phase
Limit in free tubulin gives a plateau phase
MT assembly balanced by disassembly
- What conditions must be met for microtubule formation?
- High free tubulin → MT polymerization
Low free tubulin → MT depolymerization
Critical concentration – amount of tubulin
available to balance MT assembly and
- Why is MT growth faster at the plus end? What is this called?
- Polarity of MTs both
structurally and chemically
Plus end grows and
lower for plus end
Simultaneous assembly at
plus end and disassembly
at minus end
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