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TY - JOUR AU - Nicholson, Karin L. AU - Munson, Mary AU - Miller, Rebecca B. AU - Filip, Thomas J. AU - Fairman, Robert AU - Hughson, Frederick M. PY - 1998 DA - 1998/09/01 TI - Regulation of SNARE complex assembly by an N-terminal domain of the t-SNARE Sso1p JO - Nature Structural Biology SP - 793 EP - 802 VL - 5 IS - 9 AB - The fusion of intracellular transport vesicles with their target membranes requires the assembly of SNARE proteins anchored in the apposed membranes. Here we use recombinant cytoplasmic domains of the yeast SNAREs involved in Golgi to plasma membrane trafficking to examine this assembly process in vitro. Binary complexes form between the target membrane SNAREs Sso1p and Sec9p; these binary complexes can subsequently bind to the vesicle SNARE Snc2p to form ternary complexes. Binary and ternary complex assembly are accompanied by large increases in α-helical structure, indicating that folding and complex formation are linked. Surprisingly, we find that binary complex formation is extremely slow, with a second-order rate constant of ∼3 M–1 s–1. An N-terminal regulatory domain of Sso1p accounts for slow assembly, since in its absence complexes assemble 2,000-fold more rapidly. Once binary complexes form, ternary complex formation is rapid and is not affected by the presence of the regulatory domain. Our results imply that proteins that accelerate SNARE assembly in vivo act by relieving inhibition by this regulatory domain. SN - 1545-9985 UR - https://doi.org/10.1038/1834 DO - 10.1038/1834 ID - Nicholson1998 ER -