Isolation of undegraded polysomes from radish cotyledons: Use of proteinase K and cycloheximide

A procedure for isolating undegraded polysomes from radish cotyledons is described. The current method for plant polysome preparation using buffers of high pH and high ionic strength was unable to prevent the breakdown of large polysomes occurring during the extraction. Proteinase K was very efficient in protecting polysomes from degradation. However, this yielded a high monosome content in the preparations. When proteinase K was combined with cycloheximide, a more satisfactory recovery of polysomes was achieved. This procedure could facilitate investigations of the in vitro protein synthesis activity and mRNA isolation in tissues possessing a high ribonuclease content.