11 Joint - Actin Based Cell Movement

Question 1

how does bacteria move in a cell?

Answer 1

uses actin filaments

Question 2

3 requirements fro actin based movement?

Answer 2

1. nucleation
   - polymerisation of actin filaments
2. Capping
   - prevent polyermerisation in a direction
3. Recycling
   - old filaments used to make monomers

Question 3

how can actin poly be unfavourable and then favourable?

Answer 3

Unfave
- producing dimers and trimers from monomers

Fave

• once a trimer - rapidly forms filament
• proteins can nucleate from fast growing end of actin

Question 4

structure of ARP 2/3 nucleating protein?

Answer 4

ARP 2/3 Complex

- made of ARP 2 and 3 which bind to - side of actin to form a nucleus [oligomer]

Question 5

structure of Gelsonin capping protein?

Answer 5

• a/b subunit

- Gelsonin - severes filament and binds to + end of actin where poly occurs

Question 6

where do capping proteins bind to on actin?

Answer 6

+ end of actin [barbed end]

Question 7

recycling proteins Cofilin and Profilin and role?

Answer 7

Cofilin

• bind to actin monomrs in ADP form [in fil]
• destabilise filament

Profilin

• binds to a ADP actin and exhnages it to ATP
• can add actin to barbed + end of a filament

Question 8

how do cofilin and profilin work together?

Answer 8

• cofilin disassembles filament [of ADP actin mobomers]
• Profilin replaces cofilin
• exchanges ADP to ATP
• now a ATPActin monomer
• added to barbed end

Question 9

difference between actin structures lamellipodia and filipodia?

Answer 9

Lamel

• actin filaments BRANCH
• new filaments added to sides of old fils]
• unbundled actin filaments
• form from nucleation of new fils and capping
• used in protrusion

Filo

• long parallel bundles of filaments
• used in sensing environment