Structure of the yeast polarity protein Sro7 reveals a SNARE regulatory mechanism

Department of Structural Biology, Stanford University School of Medicine, 299 Campus Drive West, Stanford, California 94305-5126, USA.
Nature (Impact Factor: 41.46). 04/2007; 446(7135):567-71. DOI: 10.1038/nature05635
Source: PubMed


Polarized exocytosis requires coordination between the actin cytoskeleton and the exocytic machinery responsible for fusion of secretory vesicles at specific sites on the plasma membrane. Fusion requires formation of a complex between a vesicle-bound R-SNARE and plasma membrane Qa, Qb and Qc SNARE proteins. Proteins in the lethal giant larvae protein family, including lethal giant larvae and tomosyn in metazoans and Sro7 in yeast, interact with Q-SNAREs and are emerging as key regulators of polarized exocytosis. The crystal structure of Sro7 reveals two seven-bladed WD40 beta-propellers followed by a 60-residue-long 'tail', which is bound to the surface of the amino-terminal propeller. Deletion of the Sro7 tail enables binding to the Qbc SNARE region of Sec9 and this interaction inhibits SNARE complex assembly. The N-terminal domain of Sec9 provides a second, high-affinity Sro7 interaction that is unaffected by the tail. The results suggest that Sro7 acts as an allosteric regulator of exocytosis through interactions with factors that control the tail. Sequence alignments indicate that lethal giant larvae and tomosyn have a two-beta-propeller fold similar to that of Sro7, but only tomosyn appears to retain the regulatory tail.

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Available from: Patrick J Brennwald, Dec 21, 2014
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    • "Studies in yeast interactome demonstrated that WD40 proteins are involved in more protein-protein interactions than any other domains [13], [14]. The functional versatility of WD40 proteins is owed to their ability, (i) to target different substrates selectively similar to F-box proteins [15] (ii) to recruit different substrates in binding modes similar to the peptide-in-groove binding of clathrin [16] or by distinct binding modes through the top and side of the WD domain as in the Gβ of the G proteins [11] (iii) to interact through insertion motifs as in MAD3 protein [17] or inter-blade binding grooves of WD40 domains for ligand binding as in Sro7 protein [18]. "
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    • "The tom-1A ΔSNARE domain (aa 1–1045 ) includes the WD40 repeats and the downstream 57 amino acid linker, based on conserved sequence alignments [24] amplified from pAB29 using primers AGAGTCATCCCTCAGAACAG and GTCTAGGATCCATGCATCGGATTCACTCCAGAACTATTC, TOPO-cloned creating pAB47. tom-1A ΔSNARE was subcloned into pAB36 containing pUNC-17 using BamH restriction sites, creating pAB48. "
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    • "The three α-helixes all interact with the WD40 domains mainly through hydrophobic interactions. Both the C-terminal tail and the insertion motif of Sro7 are involved in stabilizing the WD40 fold and tying up the two WD40 domains together (Hattendorf et al., 2007). Interestingly, neither of two WD40 propellers in Sro7 has the " velcro " closure. "
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