|
|
|
|
|
|
|
||
J. Cell Biol.,
Volume 140, Number 1, January 12, 1998 61-69
* Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755-3844; and Homotypic vacuole fusion in yeast requires
Sec18p (N-ethylmaleimide-sensitive fusion protein
[NSF]), Sec17p (soluble NSF attachment protein
[ Medical Research
Council, Laboratory of Molecular Biology, Cambridge CB2 2QH, United Kingdom
-SNAP]), and typical vesicle (v) and target membrane (t) SNAP receptors (SNAREs). We now report
that vacuolar v- and t-SNAREs are mainly found with
Sec17p as v-t-SNARE complexes in vivo and on purified vacuoles rather than only transiently forming such
complexes during docking, and disrupting them upon
fusion. In the priming reaction, Sec18p and ATP dissociate this v-t-SNARE complex, accompanied by the release of Sec17p. SNARE complex structure governs
each functional aspect of priming, as the v-SNARE regulates the rate of Sec17p release and, in turn, Sec17p-dependent SNARE complex disassembly is required
for independent function of the two SNAREs. Sec17p
physically and functionally interacts largely with the
t-SNARE. (a) Antibodies to the t-SNARE, but not the
v-SNARE, block Sec17p release. (b) Sec17p is associated with the t-SNARE in the absence of v-SNARE,
but is not bound to the v-SNARE without t-SNARE.
(c) Vacuoles with t-SNARE but no v-SNARE still require Sec17p/Sec18p priming, whereas their fusion
partners with v-SNARE but no t-SNARE do not.
Sec18p thus acts, upon ATP hydrolysis, to disassemble
the v-t-SNARE complex, prime the t-SNARE, and release the Sec17p to allow SNARE participation in
docking and fusion. These studies suggest that the analogous ATP-dependent disassembly of the 20-S complex
of NSF, -SNAP, and v- and t-SNAREs, which has
been studied in detergent extracts, corresponds to the
priming of SNAREs for docking rather than to the fusion of docked membranes.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
