Characteristics of a cell-free assay for the delivery of proteins to the plasma membrane.

We have previously described the reconstitution, in a cell-free system, of the constitutive delivery of a newly synthesized protein, influenza neuraminidase, to the plasma membrane in BHK cells. Here we report some of the characteristics of this in vitro membrane fusion event. We show that fusion requires ATP hydrolysis, and exploit this requirement to distinguish the time-course of fusion from that of neuraminidase action. In addition, we present evidence for the occurrence of multiple fusions between hybrid membrane vesicles.