About Capping Protein:
Capping proteins (CAP) control the access to the barbed ends of an actin filament. As a result, it is a really important factor in actin filament elongation. Capping proteins also have a positive relationship with barbed ends, and due to the micromolar concentration in the cytoplasm, it means that the majority of barbed ends are then capped. Any depletion of capping proteins means that there is an increased gathering of filaments that go away from the leading migrating cells. Some in-vitro experiments have shown that this then results in a loss of lamellipodia, but leads to an increase in the formation of filopodia.
Capping Protein Mechanism
When there is formation of filopodia, the barbed end of a filament is only able to extend if the ends of a filament start to fluctuate away from the membrane. This helps to incorporate new actin monomers. As a result of this occurring, the barbed ends can start to bind together by heterodimeric capping proteins. The majority of capping proteins are concentrated at the leading end, where they start to create the monomeric G-actin pool. This helps to control the length of the actin filaments, as well as the density of them. The actin filament system itself is a very important part of the cytoskeleton in the eukaryotic cells. It is both a dynamic network as well as a static structure, that can change and rearrange. In fact, it is thought to be a prominent feature in processes like cell movement, muscle contractions, and even in the process of phagocytosis.