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Two syntaxin homologues in the TGN/endosomal system of yeast
Author(s) -
Holthuis Joost C.M.,
Nichols Benjamin J.,
Dhruvakumar Sadhana,
Pelham Hugh R.B.
Publication year - 1998
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/17.1.113
Subject(s) - biology , endosome , yeast , syntaxin , genetics , microbiology and biotechnology , computational biology , membrane protein , membrane , cell
Intracellular membrane traffic is thought to be regulated in part by SNAREs, integral membrane proteins on transport vesicles (v‐SNAREs) and target organelles (t‐SNAREs) that bind to each other and mediate bilayer fusion. All known SNARE‐mediated fusion events involve a member of the syntaxin family of t‐SNAREs. Sequence comparisons identify eight such proteins encoded in the yeast genome, of which six have been characterized. We describe here the remaining two, Tlg1p and Tlg2p. These have the expected biochemical properties of t‐SNAREs, and are located in separable compartments which correspond to a putative early endosome and the yeast equivalent of the TGN, respectively. They co‐precipitate with the v‐SNARE Vti1p, which is implicated in Golgi–endosome traffic and, remarkably, binds to five different syntaxins. Tlg1p also binds the plasma membrane v‐SNARE Snc1p. Both Tlg1p and Tlg2p are required for efficient endocytosis and to maintain normal levels of TGN proteins. However, neither is required for intra‐Golgi traffic. Since no further syntaxins have been identified in yeast, this implies that the Golgi apparatus can function with a single syntaxin, Sed5p.