Lecture 15 and 16 Flashcards
What is the diameter of microtubules?
25nm outer
15nm inner
What are the monomers of microtubules?
alpha and beta tubulin
What is the diameter of microfilaments?
7nm
What are the monomers of microfilaments?
G actin
What is the diameter of intermediate filaments?
8-12nm
Name some intermediate filaments.
Keratins, vimentin, desmin, nuclear lamins
What are the two types of microtubules?
Cytoplasmic and axonemal
What do cytoplasmic microtubules do?
Regulation of cell shape
Formation of mitotic spindle
Vesicle transport
What do axonemal microtubules do?
Cell motility and signalling hub
Where are axonemal microtubules found?
Basal bodies, cillia, flagella
What are the three stages of microtubule polymerisation?
Nucleation, elongation, plateau (treadmilling)
Microtubule growth is _____ dependent.
Concentration
What is critical concentration?
The tubulin concentration at which MT assembly is balanced with dissaembly
What is the name given to the model in which one population of MT’s grow and others shrink by depolymerization?
Dynamic instability
What are the names given to the growth and shrinkage periods of MT’s?
Catastrophe and resuce
What causes dynamic instability?
GTP cap is hydrolysed, leading to catastrophe
What is the structure of a centriole?
Barrel shaped, 9 tubulin triplets, surrounded by pericentriole material
Name 3 microtubule stabilizing/bundling proteins.
tau
MAP2
+-TIP proteins
Name 3 microtubule detabilizing/severing proteins.
Stathmin/Op18
Catastophins
Katanins
Name two MT inhibiting drugs.
Colchicine (promotoes disassembly)
Nocodazole (inhibits MT assembly)
What are 4 roles of microfilaments?
Muscle contraction
Intracellular tension/cell shape
Cell migration (lamellar and amoeboid movement)
Cytoplasmic transport
What are the types of monomer that make up microfilamnets?
Alpha actin (muscle specific) Beta and gamma actin (all cells)
What protein binds ATP actin and promotes polymerisation/
Profilin
What protein binds ATP actin and blocks polymerisation?
Thymosin
What protein promotes nucleation and branching in actin filaments?
Arp2/3
What do formins do?
Bind actin filaments and promote elongation
What do capping protiens do?
Binds the end of a filament and prevent further loss/addition of subunits (e.g. CapZ)
What binds G-actin and F-actin and also severs filaments?
ADF/cofilin
What receptors ljnk cells to the extracellular matrix?
Integrin
What receptors link cells to other cells?
Cadherin
What are two classes of cadherin?
Adherens junctions (link to microfilamnets) and desmosomes (link to intermediate filaments)
What are the two major eukaryotic motility systems?
Interactions between motor proteins and microtubules
Interactions between actin and myosin motor proteins
What proteins transport towards the minus end of MTs
Dynein
What proteins transport towards the plus end of MTs?
Kinesins
What three parts do kinesins consist of?
Globular head
Coiled helical region
Light chain region
How do kinesins move?
Walk: ATP hydrolysis brings foot to bind new beta-tubulin subunit
How long are cilia?
2-10 micrometers
How long are flagella?
10-200 micrometers
What name is given to the shared structure of cilia and flagella?
Axoneme
What is the structure of the axoneme?
9+2 structure, separated by 9 dynein molecules
How does dynein generate bending of cilia/flagella?
Sliding microtubule model: ATP hydrolysis of denein
How many types of myosins are there?
24
What myosin doesn’t move towards the plus end of f-actin?
myosin VI
Which myosin walks along actin?
Myosin II
What three proteins do thin filaments in muscles contain?
F-actin, tropomyosin and troponin
Why is muscle contraction calcium dependent?
Calcium binds to a protein on tropomyosin, which changes conformation to reveal myosin binding site
What is the prokaryotic homologue to tubulin?
FtsZ protein (involved in division regulation)
What is the bacterial relative of the intermediate filament?
Crescentin (cell shape)
What is similar to actin microfilaments in bacteria?
MreB protein (cell shape)
