Ac. Chakrabarti et al., PRODUCTION OF RNA BY A POLYMERASE PROTEIN ENCAPSULATED WITHIN PHOSPHOLIPID-VESICLES, Journal of molecular evolution, 39(6), 1994, pp. 555-559
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.