N-terminal ADF domain of twinfilin and related proteins
Actin depolymerization factor/cofilin-like domains (ADF domains) are present in a family of essential eukaryotic actin regulatory proteins. Twinfilin contains two ADF domains, and inhibits the assembly of actin filaments by strongly interacting with monomeric ADP-actin (ADP-G-actin) in a 1:1 stochiometry (with it's C-terminal ADF domain, Twf-C) and inhibiting the actin monomer's nucleotide exchange. Mammalian twinfilin may also cap the barbed ends of F-actin filaments and prevent further assembly (or disassembly), in a process which requires both ADF domains. The N-terminal ADF domain (Twf-N) binds G-actin with a lower affinity than Twf-C; Twf-C can also bind F-actin. During capping, Twf-N may interact with the terminal actin subunit, and Twf-C may bind between two adjacent subunits at the side of the filament.
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