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45 Cards in this Set

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Function of cytoskeleton X 2
1.) Cell shape and structure
2.) Mechanochemical movement
The three basic filaments of cytoskeleton
1.) Actin
2.) Microtubules
3.) Intermediate filament
How are filament systems held together?
By weak non-covalent bonds
Describe the types of IF's involved in cell to cell adhesion.
1.) Desmosomes (connection between cells)
2.) Hemidesmosomes (connection between cells and matrix)
3.) Keratin (connection between cells and organelles)
Describe the types of IF's involved in muscles.
DESMINS provide a scaffold cage for skeletal muscles.
Common IF structural similarities.
1.) Globular amino-terminal domain. (HEAD)
2.) Central alpha helical domain. (BODY)
3.) Globular C-terminus domain. (TAIL)
How does IF's initially begin folding?
As coiled coil dimers.
Different types of IF coiled coil dimers.
1.) Homopolymeric
2.) Heteropolymeric
Where are the modifications (dissociations) and regulations occuring on IF's?
On the C-terminus ends
Why are hair keratins so stable and insoluble?
Due to high cysteine residues on the end forming disulfide crosslinks.
IF's are composed of what subunits?
IF's consist of 4 PROTOFIBRILS
What are protofibrils composed of?
Protofibrils composed of 2 APOLAR PROTOFILAMENTS
What are the apolar protofilaments composed of?
Apolar Protofilaments composed of 2 polar coiled coil dimers in antiparallel tetramer form
Individual coiled coiled domains have what type of repeat?
heptad
Why do IF's not have the dynamic nature of actins or microtubules?
Due to lack of polarity.
What are the benefits of IF's in regards to actin or myosin?
Greater combo of strength, stability, and flexibility.
For the most part, how are IF's regulated?
By phosphorylation (sometimes by proteolysis)
in globular region.
What enzyme breaksdown IF's in nucles?
Cyclin-dependent Kinase (CDK)
What enzyme is responsible for IF assembly?
Protein Phosphatase I (PP1)
Functions of IF's X 2.
1.) Mechanical(protection and structure)
2.) Non-mechanical (stress sensor and signaling)
Two diseases associated with gene mutations affecting the mechanical mechanism of IF.
1.) EBS (Epidermolysis Bulbosis Simplex)
2.) EH (Epidermolysis Hyperkeratosis)
Disease associated with defect in LMNA gene.
Hutchingson-Gilford Progeria
What are the globular, nucleotide-binding protein subunits in actin?
Actin monomers
What are the globular, nucleotide-binding protein subunits in microtubules?
Alpha and beta tubulin heterodimers.
Describe the ends of actin.
Barbed polar (+) end

Pointed polar (-) end
Describe the ends of microtubules.
Just (+) and (-) ends
Nucleotide binding for actin?
ADP/ATP
Nucleotide binding for microtubules?
GDP/GTP
Where do you find actins X 6?
1.) Muscle
2.) Microvilli of intestintal brush border
3.) Movement/Growth of Cell
4.) Cleavage Furrow of cytokinesis
5.) Vesicle movement
6.) Stero cilia in ear.
What are the two forms that actin can exist as?
1.) Parallel bundles
2.) 2D or 3D networks
Two important concepts of actin.
1.) Dynamic polymerization/depolymerization.
2.) Association with molecular motors.
Why is nucleation of a helical polymer difficult?
Because you need multiple and simultaneous contacts. You need at least three to spontaneously join to get the required fourth.
What causes the rate limiting for polymerization in actin?
Concentration of polymers
What are the principles that govern actin dynamics?
1.) Regulation of Bound nucleotide.
2.) Regulation of Elongation
3.) Regulation of Nucleation
4.) Regulation of Severing filaments.
Describe Regulation of Bound Nucleotide.
Factors that facilitate ADP/ATP exchange on actin....
and GDP/GTP exchange on microtubules.
Describe Elongation regulation.
Factors that alter rate of elongation?
Give an example of protein that regulates bound nucleotides?
PROFILIN facilitates ADP/ATP exchange in actin.
Give an example of Elongation regulation protein?
End-specific capping proteins.
Describe regulation of nucleation?
Proteins that regulate nucleation.
Provide example of nucleation regulation protein.
Arp complex
Describe regulation of severing filaments.
Proteins that sever filament in middle
Provide example of regulation protein that severs filaments.
Gelsolin
Give an example of non-mechanical function of IF's.
Wound signalling for healing
In regards to LMNA, what is the reason for disease phenotypes such as Progeria?
Accumulation of farnesylated Lamin A.
What is the most abundant type of protein in cell?
Actin