Sed5p selectively forms ternary and quaternary
complexes in vitro with the SNAREs Sft1p, Bet1p, Gos1p, Bos1p, Ykt6p,
and Sec22p. Proteins were resolved by SDS-PAGE, transferred to
nitrocellulose membranes, and recombinant (His)6-tagged
SNAREs detected by immunostaining with the anti-(His)6
antibody BMG-His-1. Ternary complexes: GST-Sft1p was mixed with various
combinations of two different (His)6-tagged SNARE proteins
as indicated (A). GST-Bet1p was mixed with various combinations of two
different (His)6-tagged SNARE proteins as indicated (B).
Quaternary complexes: Either GST-Bet1p or GST-Sft1p was mixed with
(His)6-Sed5p and various combinations of two other
(His)6-tagged SNARE proteins as indicated (C).
Immunoblot analysis of aliquots of soluble lysates from
bacteria expressing the (His)6-SNAREs used in this
experiment (corresponding to ∼5% of input) (D). (E) Longer exposure
of a subsection of B reveals some association of Ykt6p with [Bet1p +
Sed5p] and of Bos1p with [Bet1p + Sed5p]. Note that in the absence
of Sed5p no detectable binding is observed between either GST-Sft1p or
GST-Bet1p and other SNAREs (A and B, lanes 5–8).