InterPro domain: IPR042276

The F-actin capping protein 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 ( IPR002189 ) and beta ( IPR001698 ). Neither of the subunits shows sequence similarity to other filament-capping proteins [ 1 ].

This entry represents the beta subunit (CAPZB) and alpha subunit (CAPZA) domain 2, whose sequence is well conserved in eukaryotic species [ 2 ]. In Drosophila, mutations of the alpha and beta subunits cause actin accumulation and subsequent retinal degeneration [ 3 ]. In humans, CAPZB is part of the WASH complex that controls the fission of endosomes [ 4 ].

1. Beta-actinin is equivalent to Cap Z protein. J. Biol. Chem. 265, 8712-5
2. Disruption of the actin cytoskeleton in yeast capping protein mutants. Nature 344, 352-4
3. Mutations in the Drosophila orthologs of the F-actin capping protein alpha- and beta-subunits cause actin accumulation and subsequent retinal degeneration. Genetics 171, 1757-65
4. The Arp2/3 activator WASH controls the fission of endosomes through a large multiprotein complex. Dev. Cell 17, 712-23