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EMBO J. 2002 Feb 1;21(3):259-69.

The Vtc proteins in vacuole fusion: coupling NSF activity to V(0) trans-complex formation.

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1
Friedrich-Miescher-Laboratorium der Max-Planck-Gesellschaft, Spemannstrasse 37-39, D-72076 Tübingen, Germany.

Abstract

The fusion of cellular membranes comprises several steps; membrane attachment requires priming of SNAREs and tethering factors by Sec18p/NSF (N-ethylmaleimide sensitive factor) and LMA1. This leads to trans-SNARE pairing, i.e. formation of SNARE complexes between apposed membranes. The yeast vacuole system has revealed two subsequent molecular events: trans-complex formation of V-ATPase proteolipid sectors (V(0)) and release of LMA1 from the membrane. We have now identified a hetero-oligomeric membrane integral complex of vacuolar transporter chaperone (Vtc) proteins integrating these events. The Vtc complex associates with the R-SNARE Nyv1p and with V(0). Subunits Vtc1p and Vtc4p control the initial steps of fusion. They are required for Sec18p/NSF activity in SNARE priming, membrane binding of LMA1 and V(0) trans-complex formation. In contrast, subunit Vtc3p is required for the latest step, LMA1 release, but dispensible for all preceding steps, including V(0) trans-complex formation. This suggests that Vtc3p might act close to or at fusion pore opening. We propose that Vtc proteins may couple ATP-dependent NSF activity to a subset of V(0) sectors in order to activate them for V(0) trans-complex formation and/or control fusion pore opening.

PMID:
11823419
PMCID:
PMC125839
DOI:
10.1093/emboj/21.3.259
[Indexed for MEDLINE]
Free PMC Article
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