Throttles and Dampers: Controlling the Engine of Membrane Fusion

Thomas H. SA¶llner Vesicles deliver cargo to targets in all parts of the cell. New findings in this issue show that two regulatory proteins, Ypt1p (a Rab-family member) and Sly1p (a Sec1-family member), bind to a SNARE protein located on the target. Rothman and SA¶llner, in their Perspective, outline how these two proteins are likely to act as a throttle and brake for the process of membrane fusion that distributes the cellular constituents to their final destinations. See the report by Lupashin and Waters in this issue on p. 1255.