first of two ATPase domains of NSF and SEC18, and similar ATPase domains
N-ethylmaleimide-sensitive factor (NSF) and Saccharomyces cerevisiae Vesicular-fusion protein Sec18, key factors for eukaryotic trafficking, are ATPases and SNARE disassembly chaperones. NSF/Sec18 activate or prime SNAREs, the terminal catalysts of membrane fusion. Sec18/NSF associates with SNARE complexes through binding Sec17/alpha-SNAP. Sec18 has an N-terminal cap domain and two nucleotide-binding domains (D1 and D2) which form the two rings of the hexameric complex. The hydrolysis of ATP by D1 generates most of the energy necessary to disassemble inactive SNARE bundles, while the D2 ring binds ATP to stabilize the homohexamer. This subfamily includes the first (D1) ATPase domain of NSF/Sec18, and belongs to the RecA-like NTPase family which includes the NTP binding domain of F1 and V1 H(+)ATPases, DnaB and related helicases as well as bacterial RecA and related eukaryotic and archaeal recombinases. The RecA-like NTPase family also includes bacterial conjugation proteins and related DNA transfer proteins involved in type II and type IV secretion.