Question

A graduate student adds actin monomers and ATP into a test tube with a buffer that resembles the cell cytosol. What else must be added to the tube to produce ADP?

a) severing protein cofilin
b) nucleating protein ARP2/3
c) cofilin and ARP2/3
d) nothing

Answer 1

No additional substance is required to produce ADP from actin monomers and ATP in a test tube resembling the cell cytosol; the hydrolysis of ATP occurs inherently as part of actin filament dynamics.

Step-by-step explanation:

To produce ADP in a tube with actin monomers and ATP, nothing additional must be added for the hydrolysis of ATP to occur. Actin filaments inherently exhibit ATPase activity when the filamentous form (F-actin) is formed, as monomers in the filament convert ATP to ADP after a certain period. Certain conditions in the test tube, such as those that resemble the cell cytosol, allow the G-actin monomers bound to ATP to polymerize, and upon their incorporation into the filament, ATP is hydrolyzed to form ADP. This process leads to a dynamic instability and the continuous turnover of actin monomers at the plus end of the filament, a phenomenon known as treadmilling.