an autophagosome associated SNARE that interacts with VAMP8 and SNAP29 and is required for fusion with the lysosome. STX17 is localized on the outer membrane of autophagosomes, but not phagophores or other autophagosome precursors, which prevents them from prematurely fusing with the lysosome. In yeast, the fusion of autophagosomes with vacuoles (the yeast equivalent of lysosomes) requires SNAREs and related proteins such as the syntaxin homolog Vam3, SNAP-25 homolog Vam7, Ras-like GTPase Ypt7, and the NSF ortholog, Sec18. Flexible substitution of components Several complexes are known to flexibly substitute one protein for another: Two Qa-SNAREs in yeasts can substitute for each other to some degree. Yeasts which lose the R-SNARE - Sec22p - automatically increase levels of a homolog - Ykt6p - and use it the same way. Although Drosophilae cannot survive the loss of the SNAP-25 component, SNAP-24 can fully replace it. And also in Drosophila, an R-SNARE not normally found in synapses can substitute for synaptobrevin. In plants SNAREs also occur in plants and some understanding of their occurrence and role has obtained. These have often been found to be essential to vesicle transport, including Zheng et al 1999's finding regarding Golgi-vacuole trafficking. Much of this study has been in Arabidopsis. References External links Single-pass transmembrane proteins Neural synapse Membrane proteins Lipoproteins Protein superfamilies Molecular neuroscience