what are dyneins?

microtubule motor protein

what is the directionality of dynein on microtubule?

• Directed toward (-) end

Function of dynein?

• *Responsible for retrograde transport

• Not similar to myosins or kinesins

What happens if  nexin is not is not incorpated onto tubules?

no bending occurs, they just slide past eachother

Dynein has how many heads?

Two-headed molecule

Which end of the dynein interacts with microtubule?

the end which interacts with microtubule is is portion of the stalk which extends out of the motor domain --> STALK

function of dynactin?

Because dynein cannot bind directly to cargo, it uses a multiprotein complex called DYNACTIN to

What is the directionality of dynein?

(-) ---> (+)

when dynein is moving on microtubule, what "state" is it in?

atp/adp+pi/none

None

Antrograde def?

toward periphery = outer boundary of cell

Def of Retograde?

Towards  middle of cell

Which motor protein is responsible for Anterograde vesicle transport of cargo on Microtubule.

examples of retrograde transport-3

Dynein mediate retrograde transport

– Elements of ER

– Late endosomes

– Lysosomes to the center of the cell

Which motor protein is responsible for Retrograde vesicle transport of cargo on Microtubule.

examples of retrograde transport-3

Kinesins mediate anterograde transport

– Mitochondria

– Lysosomes to cell periphery

– Membrane vesicles

What are the 3 structures that Microtubules form?

1. Centrosome

2. Flagella

3. Cilia

How does Microtubule form?

It originates from the MTOC (mictubule organizing center)

ex. sun radiating light/ or to of hand with fingers radiating outward (microtubule)

Function of Centrosome?

1. serves as the main microtubule organizing center (MTOC)

2. regulator of cell-cycle - MITOSIS

Centriole

barrel shaped cell structure which organizez the spindle apparatus on which the chromosomes move during mitosis

Similaries and differences between flagella and cilia?

Same structure, different beating pattern:

3 components of flagella and cilia?

Basal body -

transitional zone- 9 doublets-9 triplets of microtubules

Axenome- 9 doublets surrounded by a central pair

Structure of Axoneme

a bundle of microtubules covered by a membrane

What part of Axoneme arrangement generates force?

Dyneins bound to outer doublets generate force

What part of Axonneme structure is responsible for stabalization?

Axoneme Structure stabilized by radial spokes

Function of Basal body of flagella and cilia?

• Basal body anchors cilium or flagellum to the cell

• Initiates growth of axoneme

How do cilia and flagella move?

• beating are produced by sliding of outer doublets relative to each other while nexin prevents microtublues from sliding

What function does Nextin serve in flagella movement?

nexin prevents microtublues from sliding--> stabalizing

What enables tubules to slide along one another for cilium bending?**

Dynein arms have ATPase activity. In the presence of ATP, they can move from one tubulin to another enabling tubules to slide along one another so the cilium can bend.

What holds "doublets" in place so sliding is limited lengthwise?

Because of the nexin and radial spokes, the doublets are held in place so sliding is limited lengthwise.

Key: nexin/ radial spokes

What happens if Nexin is removed?

• No bending occurs

• Causes microtubules to slide past each

How is movement of flagella and cilia described?

flagella- wavessssss

cilia- beatingg

DIfferences between Eukaryotic abd bacterial flagella?

(3)

1.  Bacterial flagella are made of flaggelin not

microtubules

2. They rotate not bend

3. They are powered by movement of protons

Where does Intermediate filaments display?

Intermediate filaments are displayed in multicellular organization

What is the function of Intermediate filaments?

  **strictly structural!

• Reinforce cells

• Distribute tensile forces across the cells in tissues

Tensile force: (stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract)

does Intermediate filaments have polarity?

NO!

How are intermediate filaments structurally described as?

 a multistrand rope

Describe the structural unit of intermediate filaments

an apolar assembly made out of "two antiparallel dimers"

apolar- having no polarity

What is the function of the monomer alpha helical rod domain?

 connects the amino (head) and carboxyl (tail)terminals

describe the stages of Intermediate filament polymerization?

1. monomer-

2. dimer

3. **tetramer- basic unit of intermediate filament

4. 2 protofilaments aggregate together to form protofibril 

5. 4 protofibril = intermediate filament

tetramer

**tetramer is the basic unit of intermediate filament

How many protofibrils is required to form 1 intermediate filament?

4

Describe formation of intermediatefilaments.

-Which ends does filament polymerize?

1. Spontaneously self assemble

2. Subunits added to both ends

Phosphorylation of head domain causes what in intermediate filaments?

Phosphorylation of the head domain depolymerizes intermediate filaments

example of where Keratin can be found?

(Type 1/2)

Epithelial cell

what are Desmosomes?

desmosomes- keratins intermediate filaments form junctions that hold cells together

What re Hemidesmosomes?

hemidesmosomes- keratin intermediate filaments that attach cells to matrix

What are desmins?

Desmins- the intermediate filaments in muscle cells  that form the desmosome (junctions that hold cells together)

What happens if skin cells or any epithelial cells lack keratin?

Loss of keratins leads to blistering, excess of hyperkeratosis ( thickening of cell)

symptoms of  epidermolysis bullosa

disrupt the filaments in the basal cells, causing mechanical fragility and cellular rupture with mild trauma, resulting in blisters

Type 4 Neurofilaments

neurofilaments are linked by plectin cross bridges to each other and to microtubules--> This adds to strength and spacing.

plectin+ microtubule + neurofilaments = increased strength and spacing.

What function does Neurofilaments provide in axons?

 Neurofilament proteins add to the diameter of the axon = larger axons---> conduct faster

Type 5 Lamins

-found

-function

- location: Nuclei of both plant/ animal cells

- function: support nuclear membrane