In molecular biology, the F-actin capping protein is a
protein complex which binds in a calcium-independent manner to the fast-growing ends of
actin filaments (barbed end), thereby blocking the exchange of subunits at these ends. Unlike
gelsolin and
severin this protein does not sever actin filaments. The F-actin capping protein is a
heterodimer composed of two unrelated subunits: alpha and beta. Neither of the
subunits shows
sequence similarity to other filament-capping
proteins.[1] The alpha subunit is a protein of about 268 to 286
amino acid residues and the beta subunit is approximately 280 amino acids, their sequences are well
conserved in
eukaryoticspecies.[2]
The actin filament system, a prominent part of the
cytoskeleton in
eukaryotic cells, is both a static structure and a dynamic network that can undergo rearrangements: it is thought to be involved in processes such as cell movement and
phagocytosis, as well as
musclecontraction.[1]