PRODUCTION OF RNA BY A POLYMERASE PROTEIN ENCAPSULATED WITHIN PHOSPHOLIPID-VESICLES

Catalyzed polymerization reactions represent a primary anabolic activi ty of all cells. It can be assumed that early cells carried out such r eactions, in which macromolecular catalysts were encapsulated within s ome type of boundary membrane. In the experiments described here, we s how that a template independent RNA polymerase (polynucleotide phospho rylase) can be encapsulated in dimyristoyl phosphatidylcholine vesicle s without substrate. When the substrate adenosine diphosphate (ADP) wa s provided externally, long-chain RNA polymers were synthesized within the vesicles. Substrate flux was maximized by maintaining the vesicle s at the phase transition temperature of the component lipid. A protea se was introduced externally as an additional control. Free enzyme was inactivated under identical conditions. RNA products were visualized in situ by ethidium bromide fluorescence. The products were harvested from the liposomes, radiolabeled, and analyzed by polyacrylamide gel e lectrophoresis. Encapsulated catalysts represent a model for primitive cellular systems in which an RNA polymerase was entrapped within a pr otected microenvironment.