MCB Lec 8

- Actin filament :thinnest
-Intermediete: strong and rigid hollow tubes
-Microtubules: bendy but hard to break

-orginizes cytoplasm and plasma support
-guides intracellular traffic(mostly Microtubules)
-Pulling apartof chromosomes in mitosis (microtubules)
- machinery for muscle cell contraction

thin and highly concentrated in the cortex, supports shape of plasma membrane

globular protien with 375 residues, contains a cleft that binds to ATP

1. G-Actin (globular), subunits add rapidly to + end
2. F-Actin, filamentoous form
3. Treadmiling: when the rate of growth =rate of shrinking
ALL OF THIS WORKS IN THE REVERSE

largest of the 3, POLYMERS of tubilin (dimer of alpha and beta subunits).
It will bind to G nucleotide

A-tubilin: inaccessible and always stays as GTP
b-tublin: more exposed to solevent and can be hydrolized from GTP>GDP

Spindle that splits chromosomes during Mitosis
When this spingle grows instead of shortening it is cancer

Vincristine: inhibits polymerazation by binding tubilin before its able to make microtubules.
Paclitaxel: stabalized the polymerized state of microtubules so chromosomes are unable to seperate

can be made from all sorts of protiens, typically fibrous (elongated

Lamins: form nuclear lamina and defines the shape of the nuclear membrane
Keratin: Helps form the skins outer layer of hair and nails

Progeria produces defective lamina because of mutated Lamin A- gene

2 a-helixes forming a left handed coil, ideal version is Heptad Repeat(many Leucine residues, in positiion 4)
Every 3.6 residues it make a turn and hydrophobic interactions coil them together

Crucial for extracellular matrix and connective tissue, 3 polypeptide chains (triple-helix), every 3rd residue is glycine
can remeber it is glycine because collagen is extremely flexible.

(Gly-Pro-Hyp)
Vitamin C is required as a cofactor for proline> hydroproline

Use ATP hydrolisis to carry out mechanical work
Act on structural elements (actin and microtubules)

Muscle contractions and intercellular transport, kinesin "walks"

Has 2 heads so ATP can bind
long tail
ATP hydrolysis drives the physical movement of myosin along the actin filimanet in contraction

1. Relaxed: release of ADP and the ATP binding alters the conformation so the actin is not connected
2. Contracted: hydrolysis of ATP> ADP+Pi and triggers the myosin to bind to actin

acts on microtubule. Looks like a big balloon with blobby feet, looks liek tis walking because the ATP binds to tubilin cite and becomes ADP