Problem 8

Unique actin-binding proteins control actin filament length and turnover rate.

 

CapZ, a protein made up of two nearly similar subunits, attaches to the positive end of an actin filament with an extremely high affinity (0.1 nM), preventing the addition or removal of subunits.

 

Trapomodulin, which attaches to the negative end of the actin filament, also prevents its formation and dissemination by binding to tropomodulin.

 

ATP/ADP exchange in G-actin is facilitated by the profilin enzyme, which also speeds up polymerization.