What is the function of CapZ in actin regulation?
Barbed end availability determines where new polymerization occurs in lamellipodia and filopodia. CapZ heterodimer alpha beta forms cap with extremely low dissociation rate half life 30 minutes in vitro. Binding interface extensive, burying 2000 square angstroms, alpha C terminal tentacle interacting with hydrophobic cleft between actin subdomains 1 and 3 of ultimate subunit, beta tentacle contacting penultimate subunit groove, physically blocking monomer docking. Quantitative fluorescence speckle microscopy shows most barbed ends in resting cells are capped, only about 5 percent free, but sec
Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 18: CapZ Barbed End Capping Function.
