Functional architecture of an intracellular membrane t-SNARE.
Lipid bilayer fusion is mediated by SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) located on the vesicle membrane (v-SNAREs) and the target membrane (t-SNAREs). The assembled v-SNARE/t-SNARE complex consists of a bundle of four helices, of which one is supplied by the v-SNARE and the other three by the t-SNARE. For t-SNAREs on the plasma membrane, the protein syntaxin supplies one helix and a SNAP-25 protein contributes the other two. Although there are numerous homologues of syntaxin on intracellular membranes, there are only two SNAP-25-related proteins in yeast, Sec9 and Spo20, both of which are localized to the plasma membrane and function in secretion and sporulation, respectively. What replaces SNAP-25 in t-SNAREs of intracellular membranes? Here we show that an intracellular t-SNARE is built from a 'heavy chain' homologous to syntaxin and two separate non-syntaxin 'light chains'. SNAP-25 may thus be the exception rather than the rule, having been derived from genes that encoded separate light chains that fused during evolution to produce a single gene encoding one protein with two helices.
Fukuda
R
R
Cellular Biochemistry & Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
McNew
J A
JA
Weber
T
T
Parlati
F
F
Engel
T
T
Nickel
W
W
Rothman
J E
JE
Söllner
T H
TH
D004926:Escherichia coli; D005656:Fungal Proteins / Q000737:chemistry / Q000502:physiology; D007425:Intracellular Membranes / Q000737:chemistry / Q000502:physiology*; D008565:Membrane Proteins / Q000737:chemistry / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D050600:SNARE Proteins; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D050825:Synaptosomal-Associated Protein 25; D033921:Vesicular Transport Proteins
D005656:Fungal Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; D050683:R-SNARE Proteins; D011993:Recombinant Fusion Proteins; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; D050825:Synaptosomal-Associated Protein 25; C107706:VAM3 protein, S cerevisiae; D033921:Vesicular Transport Proteins; C107127:YKT6 protein, S cerevisiae