This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Ypt/Rab GTPases are conserved key regulators of all steps of intracellular trafficking. They act by cycling between the GTP "on" and the GDP "off" states. This cycling is regulated in turn by upstream regulators: GEFs and GAPs. At the "on" state Ypt/Rabs interact with effectors that mediate vesicular transport. We focus on Ypt31/32, Ypt/Rab GTPases responsible for secretory vesicle exit from trans-Golgi network, looking for their effectors and their mode of action on these effectors, as well as their upstream regulators. We would like to use FRET for these purposes.