Variations in Brain Cortical Polysome Translation Products Among Rats of the Same Strain

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Abstract
Studies were undertaken to determine whether there exist variations among the translation products of polysomes from different brains of animals of the same strain. Polysomes were prepared from individual rat cortices and translated in a reticulocyte protein‐synthesizing system containing rabbit reticulocyte factors and l‐[35S]methionine; the resulting radioactive proteins were analyzed by two‐dimensional polyacrylamide gel electrophoresis autoradiography. Comparison of the autoradiographs revealed that two acidic proteins, A and B, of apparent 54,000 M. W. occur as three phenotypes: A only, B only, or A plus B. These proteins were not detectable by Coomassie brilliant blue staining of two‐dimensional electrophoretograms of brain protein preparations. Messenger RNA was extracted from pooled cortices and translated in a wheat germ extract, and both A and B proteins were detected among the products of translation. Cyclic AMP affinity chromatography of the translation products of cortical polysomes showed that both A and B proteins bind to cyclic AMP. Our data are consistent with the conclusion that there are qualitative differences in the polysome translation products that bind to cyclic AMP among individual cortices of rats of the same strain.