Please answer all the parts of the question. (A) NO ADDED PROTEIN 2. You have di
ID: 189642 • Letter: P
Question
Please answer all the parts of the question.
(A) NO ADDED PROTEIN 2. You have discovered two proteins that bind microfilaments. To determine whether either protein affects actin polymerization, you measure microfilament formation as a function of actin concentration in the absence of both proteins, in the presence of protein 1, and in the presence of protein 2. The data are shown to the right. (50 points) filament a. How does protein 1 behave? How can you tell? (15 points) mass monomer 0 0.20,4 0.6 0.8 actin concentration (uM) (B) PROTEIN 1. b. What is an example of a cellular protein that behaves like protein 1 does here? (10 points) filament mass c. How does protein 2 behave? How can you tell? (15 points) monomer 0 0.20.40.60,8 actin concentration (UM) (C) PROTEIN 2 monomer d. What is an example of a cellular protein that behaves like protein 2 does here? (10 points) mass filament 0 0.20.40.6 0.8 actin concentration (uM)Explanation / Answer
Globular actins polymerize to form actin filaments. These actin filaments occur as microfilaments in the cytoskeleton. Actin polymerization occurs in three stages.
The first stage is known as a lag period during which the actin monomers aggregates into short, unstable oligomers containing 3-4 subunits. The formation of filaments starts when the monomer concentration reaches a certain level known as critical concentration.
The second stage includes rapid elongation of these oligomers into a filament by the addition of actin monomers to both of its ends.
This third stage is called steady state because in this stage equilibrium state occurs. In this stage, as the filaments grows, the concentration of monomers decreases until it is in equilibrium with the filament.
Now, in Figure A, - No protein added
When no protein is added, the critical concentration of monomer (Cc) is 0.3µM. This means that filament formation starts, when the concentration of 0.3µM for the actin monomer is reached.
Now in Figure B – Protein 1 added
When ‘protein 1’ is added, the critical concentration of monomer (Cc) decreases to 0.12µM. Thus, the filament formation starts earlier as compared to when ‘no protein’ is added and also at much lower critical concentration of monomer than that required when ‘no protein’ is added.
The cellular protein which acts as protein 1 is Profilin.
Now in Figure C – Protein 2 added
When ‘protein 2’ is added, the critical concentration of monomer (Cc) decreases to 0.6µM. Thus, the filament formation is suppressed. The high critical concentration of monomer kick starts the very late filament formation. Depolymerisation of filament occurs to maintain the high critical monomer concentration and hence filament formation is suppressed.
The cellular protein which acts as protein 2 is thymosin 4.