Convergence and divergence in the mechanism of SNARE binding by Sec1/Munc18-like proteins.
Sec1Munc18-like (SM) proteins functionally interact with soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNARE) in membrane fusion, but the mechanisms of these interactions differ. In vertebrates, SM proteins that mediate exocytosis (Munc18-1, 18-2, and 18c) bind to the closed conformation of syntaxins 1-4, which requires the N-terminal H(abc) domains and SNARE motifs of these syntaxins. In contrast, SM proteins that mediate Golgi and endoplasmic reticulum fusion (Sly1 and Vps45) bind only to short N-terminal sequences of syntaxins 5, 16, or 18, independently of their H(abc) domains and SNARE motifs. We now show that Munc18-1, Sly1, and Vps45 interact with cognate syntaxins via similar, autonomously folded N-terminal domains, but the syntaxin 5-binding surface of the Sly1 N-terminal domain is opposite to the syntaxin 1-binding surface of the Munc18-1 N-terminal domain. In transfected cells, the N-terminal domain of Sly1 specifically disrupts the structure of the Golgi complex, supporting the notion that the interaction of Sly1 with syntaxin 5 is essential for fusion. These data, together with previous results, suggest that a relatively small N-terminal domain of SM proteins is dedicated to mechanistically distinct interactions with SNAREs, leaving the remaining large parts of SM proteins free to execute their as yet unknown function as effector domains.
Dulubova
Irina
I
Department of Biochemistry, University of Texas Southwestern Medical Center, 6000 Harry Hines Boulevard, Dallas 75390, USA.
Yamaguchi
Tomohiro
T
Arac
Demet
D
Li
Hongmei
H
Huryeva
Iryna
I
Min
Sang-Won
SW
Rizo
Josep
J
Sudhof
Thomas C
TC
D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D008565:Membrane Proteins / Q000378:metabolism*; D008958:Models, Molecular; D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011506:Proteins / Q000378:metabolism*; D050765:Qa-SNARE Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D050600:SNARE Proteins; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D014162:Transfection; D014709:Vero Cells; D033921:Vesicular Transport Proteins
D002352:Carrier Proteins; D008565:Membrane Proteins; D051938:Munc18 Proteins; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D011506:Proteins; D050765:Qa-SNARE Proteins; D011993:Recombinant Fusion Proteins; C497931:SEC1 protein, S cerevisiae; C072520:SLY1 protein, S cerevisiae; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins