Biochemistry and regulation of rubber transferase in parthenium argentatum gray

Abstract

Washed rubber particles from stem homogenates of Parthenium argentatum contain a bound rubber transferase which catalyzes the de novo synthesis of a rubber polymer. The bound rubber transferase utilizes the photolabile substrate analogs 2- diazo-3-trifluropropionyloxy-dimethylallyl pyrophosphate and 2- diazo-3-trifluropropionyloxy-geranyl pyrophosphate as allylic cosubstrates for the polymerization reaction. Irradiation of the washed rubber particles with UV light in the presence of Mg2+, isopentynyl pyrophosphate and 2-diazo-3-trifluropropionyloxygeranyl pyrophosphate photo inactivates the rubber transferase. Irradiation of the washed rubber particles with UV light in the presence of Mg2+, isopentynyl pyrophosphate and 8 -[3H ]-2- diazo-3-trifluropropionyloxy-geranyl pyrophosphate labels mainly a polypeptide with a molecular weight of 52,000 as determined by the separation of the extracted protein by sodium dodecyl polyacrylamide gel electrophoresis. The bound rubber transferase was solubilized from the rubber particles with 3-[(cholamidopropyl)dimethylammonio]-1-propane sulfonate and purified. A 52 kD protein represented as a major protein in the sodium dodecyl polyacrylamide gel electrophoresis. These studies, together with the photoaffinity labeling studies, tentatively show the molecular weight of the purified bound rubber transferase to be 52,000. The purified rubber transferase catalyzed the formation of a high molecular weight rubber polymer. Washed rubber particles isolated from Hevea brasiliensis contain a tightly bound rubber transferase capable of catalyzing the de novo synthesis of polyisoprene. Experiments with photoprobe substrates, similar to Parthenium argentatum was performed using the washed rubber particles of Hevea brasiliensis. From these studies a polypeptide of 94 kD has been tentatively identified to be the rubber transferase in Hevea brasiliensis. Rubber transferase activity in stem bark tissue of Parthenium argentatum increased several fold by exposure of the plants to low w inter temperatures. Sodium dodecyl polyacrylamide gel electrophoresis shows that the washed rubber particles proteins were higher in cold induced plant than the plants that were not exposed to cold temperature...