LMA1 binds to vacuoles at Sec18p (NSF), transfers upon ATP hydrolysis to a t-SNARE (Vam3p) complex, and is released during fusion

Cell. 1998 Jun 26;93(7):1125-34. doi: 10.1016/s0092-8674(00)81457-9.


Vacuole fusion requires Sec18p (NSF), Sec17p (alpha-SNAP), Ypt7p (GTP binding protein), Vam3p (t-SNARE), Nyv1p (v-SNARE), and LMA1 (low Mr activity 1, a heterodimer of thioredoxin and I(B)2). LMA1 requires Sec18p for saturable, high-affinity binding to vacuoles, and Sec18p "priming" ATPase requires both Sec17p and LMA1. Either the sec18-1 mutation and deletion of I(B)2, or deletion of both I(B)2 and p13 (an I(B)2 homolog) causes a striking synthetic vacuole fragmentation phenotype. Upon Sec18p ATP hydrolysis, LMA1 transfers to (and stabilizes) a Vam3p complex. LMA1 is released from vacuoles in a phosphatase-regulated reaction. This LMA1 cycle explains how priming by Sec18p is coupled to t-SNARE stabilization and to fusion.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphatases*
  • Adenosine Triphosphate / metabolism
  • Amino Acid Sequence
  • Enzyme Inhibitors / pharmacology
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Glycoproteins / genetics
  • Glycoproteins / metabolism*
  • Hydrolysis
  • Membrane Fusion / physiology*
  • Membrane Proteins*
  • Microcystins
  • Molecular Sequence Data
  • Mutation
  • Peptides, Cyclic / pharmacology
  • Phosphoprotein Phosphatases / antagonists & inhibitors
  • Phosphoproteins
  • Protein Binding
  • Qa-SNARE Proteins
  • Saccharomyces cerevisiae / cytology
  • Saccharomyces cerevisiae Proteins*
  • Thioredoxins / metabolism*
  • Vacuoles / metabolism*
  • Vesicular Transport Proteins*


  • Enzyme Inhibitors
  • Fungal Proteins
  • Glycoproteins
  • Membrane Proteins
  • Microcystins
  • Peptides, Cyclic
  • Phosphoproteins
  • Qa-SNARE Proteins
  • Saccharomyces cerevisiae Proteins
  • VAM3 protein, S cerevisiae
  • Vesicular Transport Proteins
  • yeast proteinase B inhibitor
  • Thioredoxins
  • Adenosine Triphosphate
  • Phosphoprotein Phosphatases
  • Adenosine Triphosphatases
  • SEC18 protein, S cerevisiae
  • cyanoginosin LR