The yeast lgl family member Sro7p is an effector of the secretory Rab GTPase Sec4p.
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.
Grosshans
Bianka L
BL
Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA.
Andreeva
Anna
A
Gangar
Akanksha
A
Niessen
Sherry
S
Yates
John R
JR
Brennwald
Patrick
P
Novick
Peter
P
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*
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