title: The yeast lgl family member Sro7p is an effector of the secretory Rab GTPase Sec4p.
abstract: Rab guanosine triphosphatases regulate intracellular membrane traffic by binding specific effector proteins. The yeast Rab Sec4p plays multiple roles in the polarized transport of post-Golgi vesicles to, and their subsequent fusion with, the plasma membrane, suggesting the involvement of several effectors. Yet, only one Sec4p effector has been documented to date: the exocyst protein Sec15p. The exocyst is an octameric protein complex required for tethering secretory vesicles, which is a prerequisite for membrane fusion. In this study, we describe the identification of a second Sec4p effector, Sro7p, which is a member of the lethal giant larvae tumor suppressor family. Sec4-GTP binds to Sro7p in cell extracts as well as to purified Sro7p, and the two proteins can be coimmunoprecipitated. Furthermore, we demonstrate the formation of a ternary complex of Sec4-GTP, Sro7p, and the t-SNARE Sec9p. Genetic data support our conclusion that Sro7p functions downstream of Sec4p and further imply that Sro7p and the exocyst share partially overlapping functions, possibly in SNARE regulation.
authors.affiliation: Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA.
authors.forename: Bianka L
authors.initials: BL
authors.lastname: Grosshans
authors.forename: Anna
authors.initials: A
authors.lastname: Andreeva
authors.forename: Akanksha
authors.initials: A
authors.lastname: Gangar
authors.forename: Sherry
authors.initials: S
authors.lastname: Niessen
authors.forename: John R
authors.initials: JR
authors.lastname: Yates
authors.forename: Patrick
authors.initials: P
authors.lastname: Brennwald
authors.forename: Peter
authors.initials: P
authors.lastname: Novick
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D008954:Models, Biological; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000378:metabolism; D050767:Qc-SNARE Proteins / Q000378:metabolism; D050600:SNARE Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D015398:Signal Transduction; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D020690:GTPase-Activating Proteins; D046912:Multiprotein Complexes; D050767:Qc-SNARE Proteins; C105132:SEC10 protein, S cerevisiae; C090117:SEC9 protein, S cerevisiae; D050600:SNARE Proteins; C116430:SRO7 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; C064320:SEC4 protein, S cerevisiae; D020691:rab GTP-Binding Proteins