Syntaxin Structure

SuEE, S., Misea, S., Saidi, L. F., and Hurley, J. H., Structure of the GAT domain of human GGAl a syntaxin amino-terminal domain fold in an endosomal trafScking adaptor, Proc. Natl. Acad. Sci. USA, 2003, 100, 4451. 

Fig. 1 Structure of the neuronal SNAREs. Upper panel domain structure of the three neuronal SNARE proteins involved in synaptic vesicle fusion. Syntaxin 1A and SNAP-25 (contains two SNARE motifs) are associated with the presynaptic membrane, whereas synaptobrevin 2 is synaptic vesicle associated. The SNARE motifs form a stable complex (core complex) whose crystal structure has been analyzed (lower panel). In the complex, each of the SNARE motifs adopts an alpha-helical structure, and the four alpha-helices are aligned in parallel forming a twisted bundle (modified from Sutton et al. 1998). Stability of the complex is mediated by layers of interaction (—7 to +8) in which amino acids from each of the four alpha-helices participate (see text).

In addition to the proteins discussed above, neuronal SNAREs were reported to interact with numerous other proteins in a specific manner, but in most cases both the structural basis and the biological function of these interactions need to be defined. For instance, synaptophysin, a membrane protein of synaptic vesicles, forms a complex with synaptobrevin in which synaptobrevin is not available for interactions with its partner SNAREs syntaxin 1A and SNAP-25, suggesting that this complex represents a reserve pool of recruitable synaptobrevin (Becher et al. 1999) or regulates interactions between the vesicle-associated synaptobrevin and the plasmalem-mal SNAREs. Alternatively, it has been suggested that this complex is involved in synaptobrevin sorting to synaptic vesicles. 

McEwen JM, Madison JM, Dybbs M, Kaplan JM (2006) Antagonistic regulation of synaptic vesicle priming by Tomosyn and UNC-13. Neuron 51 303-15 Misura KM, Scheller RH, Weis WI (2000) Three-dimensional structure of the neuronal-Secl-syntaxin la complex. Nature 404 355-62... 

In this chapter, we will review the current knowledge of the role of LPS as a M AMP in plant innate immunity. We will give an overview of the range of responses induced by LPS, the sub-structures within LPS that are recognized by plants and variations within the LPS structure that can alter its activity as a MAMP. We will go on to discuss new work that suggests a role for the plasma-membrane resident syntaxin PEN1 in transduction of the LPS signal. 

SNARE proteins assemble into a heterotrimeric SNARE complex (or core complex). The crystal structure of the core complex revealed a bundle of four a-helices, one each contributed by synaptobrevin and syntaxin and two contributed by SNAP-25 (28). The process of SNARE complex assembly proceeds from N-terminal to C-terminal direction in what is commonly referred to as a zippering action, which brings the C-terminal membrane anchors of the transSNAREs together (29). This action is proposed to force the closely apposed membranes together to initiate fusion. 

In another application, STED microscopy also revealed the ring-like structure of the protein hruchpilot at synaptic active zones in the drosophila neuromuscular junction [90], Further studies included the visualization of the spatial distribution of the SNARE protein syntaxin [91], the nuclear protein SC35 [85], and the nicotinic acetylcholine receptor [92]. IsoSTED microscopy resolved the tube-like 3D-distribution of the TOM20 protein complex in the mitochondria in a mammalian cell [87]. 

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