Structure::SNARE (protein)

::concepts

Journal::snare    Membrane::fusion    Title::volume    Pages::proteins    Complex::snap-    Issue::vauthors

Structure SNAREs are small, abundant, tail-anchored proteins which are often post-translationally inserted into membranes via a C-terminal transmembrane domain. Seven of the 38 known SNAREs, including SNAP-25, do not have a transmembrane domain and are instead attached to the membrane via lipid modifications such as palmitoylation.<ref>{{#invoke:Citation/CS1|citation |CitationClass=journal }}</ref> ). Tail-anchored proteins can be inserted into the plasma membrane, endoplasmic reticulum, mitochondria, and peroxisomes among other membranes, though any particular SNARE is targeted to a unique membrane. The targeting of SNAREs is accomplished by altering either the composition of the C-terminal flanking amino acid residues or the length of the transmembrane domain. Replacement of the transmembrane domain with lipid anchors leads to an intermediate stage of membrane fusion where only the two contacting leaflets fuse and not the two distal leaflets of the two membrane bilayer.<ref>{{#invoke:Citation/CS1|citation |CitationClass=journal }}</ref>

Although SNAREs vary considerably in structure and size, all share a segment in their cytosolic domain called a SNARE motif that consists of 60-70 amino acids and contains heptad repeats that have the ability to form coiled-coil structures. V- and t-SNAREs are capable of reversible assembly into tight, four-helix bundles called "trans"-SNARE complexes. In synaptic vesicles, the readily-formed metastable "trans" complexes are composed of three SNAREs: syntaxin 1 and SNAP-25 resident in cell membrane and synaptobrevin (also referred to as vesicle-associated membrane protein or VAMP) anchored in the vesicle membrane.

In neuronal exocytosis, syntaxin and synaptobrevin are anchored in respective membranes by their C-terminal domains, whereas SNAP-25 is tethered to the plasma membrane via several cysteine-linked palmitoyl chains. The core trans-SNARE complex is a four-<math>\alpha</math>-helix bundle, where one <math>\alpha</math>-helix is contributed by syntaxin 1, one <math>\alpha</math>-helix by synaptobrevin and two <math>\alpha</math>-helices are contributed by SNAP-25.

The plasma membrane-resident SNAREs have been shown to be present in distinct microdomains or clusters, the integrity of which is essential for the exocytotic competence of the cell.


SNARE (protein) sections
Intro   Types    Structure    Membrane fusion    Components    Mechanism of membrane fusion   Regulatory Effects on Exocytosis   Toxins    Role in neurotransmitter release    Role in autophagy   References  External links  

Structure
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