CRYSTAL-STRUCTURE OF THE HEXAMERIZATION DOMAIN OF N-ETHYLMALEIMIDE-SENSITIVE FUSION PROTEIN

N-ethylmaleimide-sensitive fusion protein (NSF) is a cytosolic ATPase required for many intracellular vesicle fusion reactions. NSF consists of an amino-terminal region that interacts with other components of t he vesicle trafficking machinery, followed by two homologous ATP-bindi ng cassettes, designated D1 and D2, that possess essential ATPase and hexamerization activities, respectively. The crystal structure of D2 b ound to Mg2+-AMPPNP has been determined at 1.75 Angstrom resolution. T he structure consists of a nucleotide-binding and a helical domain, an d it is unexpectedly similar to the first two domains of the clamp-loa ding subunit delta' of E. coli DNA polymerase III. The structure sugge sts several regions responsible for coupling of ATP hydrolysis to stru ctural changes in full-length NSF.