Polysomes from Krebs II ascites and 3T3 cells were separated into three populations by using a sequential extraction method. Free polysomes were released by using a combination of low salt (25 mM KCl) and NP-40 detergent in the lysis buffer. The cytoskeletal bound polysomes were subsequently released by raising the salt concentration to 130 mM and finally, polysomes bound to the membranes of the endoplasmic reticulum were extracted by the combined treatment with Triton X-100 and deoxycholate. The results presented here illustrate that the three polysome-containing fractions differ in many parameters such as polysome profiles, cytoskeletal components and phospholipid content. When polyA-containing mRNA was isolated from the three polysome fractions and translated in an in vitro system, some differences were observed in the patterns of proteins being synthesized.
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