What are the 3 types of cell skeletons
- Microfilaments
- Intermediate filaments
- Microtubules
Describe microfilaments
- diameter
- consists of
- function
- 7-9nm
- consists of actin
- a) cytokinesis, separation of daughter cells AFTER MITOSIS
b) muscle contraction
c) cell shape
Describe intermediate filaments
- diameter
- consists of
- function
- 10nm
- consists of keratins (in epithelial cells) or vimentin
- a) growth of nerve axons
b) stability of cells against mechanical forces
Describe microtubules
- diameter
- consists of
- function
- 24nm
- consists of tubulin
- a) orientation of chromosomes in the equatorial plane during metaphase and separation into daughter cells during mitosis
b) intracellular traffic
c) cell motility either by cilia or by crawling
d) organization of cell wall in plants and yeasts
Describe the basic actin structure (makes microfilament)
- F-actin (filamentous actin) filaments are constructed from G-actin (globular actin) monomers.
- Actin fibers are an important component of muscle and make up the outer structural support of cells.
G-actin protein polymerizes to ___-actin
F-actin
What are the 2 actin binding proteins
- Gelsolin
2. Profilin
Example of a molecule that binds actin and affects polymerization?
- The poison PHALLOIDIN
- a bicyclic peptide isolated from the death cap mushroom Amanita phalloides
Describe the structure of intermediate filament
Central coiled-coil region (containing HEPTAD repeats) of the IF protein is ~300 AAs long. N-, C- terminal domains help form the coiled-coil dimer.
What are 4 examples of IF?
- Keratin
- Vimentin
- Neurofilament proteins
- Nuclear lamins
Fxn of alpha-keratin? How many genes?
- Keratin is the protein that protects epithelial cells from damage or stress.
- It is the key structural material making up the outer layer of human skin.
- Keratins: ~60 human genes
- Mutations can cause diseases
What are coiled coils? Example?
- Coiled coils are two alpha helices twisted together into a SUPER helix e.g. keratin
- side chain interactions btwn alpha-helices r maximized by wrapping helices around each other (super-coil or coiled coil)
- 3.6 residue per turn leads to heptad repeat
Example of heptad repeat
- L-zipper
- a-keratin
Which are more common, parallel or parallel helices?
Parallel
Is alpha-helix parallel or antiparallel
Parallel
What does the [cysteines] in helices suggest
- High [Cysteine, disulfides] in a-keratin
- high [Cys] = hard (nails), low [Cys] = soft
Slide 13
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What are the 4 things microtubules are involved in?
- Beating of cilia and flagella.
- Vesicle transport in the cell and phagocytosis.
- Formation of the mitotic spindle.
- Stabilization of cell shape, elasticity of erythrocytes and the stability of the long axons in nerve cells.
- Keeping of cell organelles such as GOLGI-apparatus, ER, and mta in their proper place.
α and β _____ proteins polymerize to microtubles
a and B Tubulin (a is minus/bottom end, beta is plus/top end)
Microtube dimers are found where? Microtubes trimers are found where?
Dimer (a + B) = cilia and flagella
Trimer (a + B + C) = found in basal bodies and centrioles
Why are microtubules target of toxins and drugs?
Cause have central role in cell division
What are 3 molecules produced by plants that are toxic to microtubules?
- Colchicine
- Vinblastine
- Paclitaxel
What are the 2 motor proteins that travel on microtubules?
- Kinesin
2. Dynein
Fxn of kinesin and dynein?
These motors pull many types of cargo through the cell, ranging from small vesicles to entire mitochondria
