Brewer…Rizo {Nat Struct Mol Biol 22: 555}
Pseudocontact shifts, induced on nuclei of the Synaptotagmin-I C2B domain (color-coded spheres) by a lanthanide ion attached to the SNARE complex, delineate the dynamic orientation of the C2B domain with respect to the four-helix bundle. The anisotropic magnetic susceptibility tensor of the lanthanide ion is represented by the red and blue isosurfaces.
Dynamic binding mode of a Synaptotagmin-1-SNARE complex in solution
Brewer KD, Bacaj T, Cavalli A, Camilloni C, Swarbrick JD, Liu J, Zhou A, Zhou P, Barlow N, Xu J, Seven AB, Prinslow EA, Voleti R, Häussinger D, Bonvin AM, Tomchick DR, Vendruscolo M, Graham B, Südhof TC, Rizo J.
Nat Struct Mol Biol. 2015 Jul; 22: 555 [Epub 1 Jun 2015].
Rapid neurotransmitter release depends on the Ca(2+) sensor Synaptotagmin-1 (Syt1) and the SNARE complex formed by synaptobrevin, syntaxin-1 and SNAP-25. How Syt1 triggers release has been unclear, partly because elucidating high-resolution structures of Syt1-SNARE complexes has been challenging. An NMR approach based on lanthanide-induced pseudocontact shifts now reveals a dynamic binding mode in which basic residues in the concave side of the Syt1 C2B-domain β-sandwich interact with a polyacidic region of the SNARE complex formed by syntaxin-1 and SNAP-25. The physiological relevance of this dynamic structural model is supported by mutations in basic residues of Syt1 that markedly impair SNARE-complex binding in vitro and Syt1 function in neurons. Mutations with milder effects on binding have correspondingly milder effects on Syt1 function. Our results support a model whereby dynamic interaction facilitates cooperation between Syt1 and the SNAREs in inducing membrane fusion.
PubMed: 26030874. Doi: 10.1038/nsmb.3035
