1. You have a mystery protein that you suspect is a regulator of actin polymeriz
ID: 219817 • Letter: 1
Question
1. You have a mystery protein that you suspect is a regulator of actin polymerization. investigate this, you acquired a few reagents: pyrene-labeled actin monomers at 1 M concentration, Mg, ATP, and you also found a fluorometer with which you can obtain the actin polymerization curve. You also have the mystery protein purified, which you can add to the polymerization reaction Sketch the curve for actin polymerization in the presence of a protein used as the control, such as bovine serum albumin (BSA). Explain what are the three phases of the curve. ( pt) a) b) Now you add your mystery protein at the initiation of actin polymerization. Sketch the curve if your protein promotes actin nucleation. Explain what is the key difference from the curve in (a). (3 pts) Sketch the curve if your mystery protein caps the barbed ends of actin filaments. Explain what is the key difference from the curve in (a). (3 pts) c) d) Sketch the curve if your mystery protein sequesters actin monomers into a polymerization incompetent state, and the molar concentration of your protein in the reaction is less than actin (so it doesn't sequester all actin). Explain what is the key difference from the curve in (a). (3 pts) 2. Dosing some actin filaments (product of the reaction in a) into a new polymerization reaction will reduce the lag phase because the added filament ends serve as nuclei for polymcrization How might you use this system to test if your mystery protein can sever actin filaments? (3 pts)Explanation / Answer
2. Actin filaments or F- actin are formed by linear polymers of globular proteins or G- actins, which gets bundled together to form actin cytoskeleton. When actin filaments enter polymerisation, it undergo three phases namely, nucleation, elongation and steady state phases. Actin filaments enter as monomers during nucleation phase and forms a nucleus. During elongation phase, these monomers are added to the positive end of the filament, with the help of formin. Finally in the steady state phase of the polymerisation, monomers destabilise from negative and polymerisation at positive ends, respectively.
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