MmuEX0019390 @ mm10

A construct composed of the C-terminal half of FRLalpha (FRLalpha-C; inclusion of MmuEX0019390) is a dimer and has multiple effects on muscle actin, including tight binding to actin filament sides (also observed for beta; skipping), partial inhibition of barbed end elongation, inhibition of barbed end binding by capping protein, acceleration of polymerization from monomers, and actin filament severing. These multiple activities can be explained by a model in which FRLalpha-C binds filament sides but prefers the topology of sides at the barbed end (end-sides) to those within the filament. This preference allows FRLalpha-C to nucleate new filaments by side stabilization of dimers, processively advance with the elongating barbed end, block interaction between C-terminal tentacles of capping protein and filament end-sides, and sever filaments by preventing subunit re-association as filaments bend. Note: it does not compare the function of alpha (inclusion) with beta (skipping) for all experiments.

[Negative results]. 293T cells transfected with FMNL1alpha (inclusion of HsaEX0026025) and FMNL1beta (skipping) showed mainly intracellular cytoplasmic distribution of FMNL1, whereas cells transfected with FMNL1gamma showed a distinct membranous FMNL1 localization as well as extensive polarized membrane protrusions and blebs. Inclusion/exclusion of HsaEX0026025 generates different C-term, as does the IR of gamma.