Sec15 interacts with Rab11 via a novel domain and affects Rab11 localization in vivo.
Sec15, a component of the exocyst, recognizes vesicle-associated Rab GTPases, helps target transport vesicles to the budding sites in yeast and is thought to recruit other exocyst proteins. Here we report the characterization of a 35-kDa fragment that comprises most of the C-terminal half of Drosophila melanogaster Sec15. This C-terminal domain was found to bind a subset of Rab GTPases, especially Rab11, in a GTP-dependent manner. We also provide evidence that in fly photoreceptors Sec15 colocalizes with Rab11 and that loss of Sec15 affects rhabdomere morphology. Determination of the 2.5-A crystal structure of the C-terminal domain revealed a novel fold consisting of ten alpha-helices equally distributed between two subdomains (N and C subdomains). We show that the C subdomain, mainly via a single helix, is sufficient for Rab binding.
Wu
Shuya
S
Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
Mehta
Sunil Q
SQ
Pichaud
Franck
F
Bellen
Hugo J
HJ
Quiocho
Florante A
FA
D000818:Animals; D003461:Crystallography; D004330:Drosophila / Q000378:metabolism*; D029721:Drosophila Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017956:Photoreceptor Cells, Invertebrate / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D033921:Vesicular Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000032:analysis* / Q000378:metabolism; D000099193:rab11 GTP-Binding Proteins
D029721:Drosophila Proteins; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C505147:Sec15 protein, Drosophila