Radioiodine labeling during protein synthesis

Abstract

Radioiodination of aminoacyl-transfer RNAs with either .sup.125 I or .sup.131 I resulted in the preferential addition of radioiodine to bound tyrosine. The radioiodinated tyrosyl-tRNA was 10-fold purified by chromatography and was found to consist essentially of monoiodo- and diiodo-tRNA in approximately equal isotopic proportions. The radioiodinated tyrosine was readily incorporated into proteins synthesized in broken cell reactions. The specific activity of the iodine-labeled proteins can be modulated up to the highest theoretical value (radioiodine in each tyrosine) yielding products that are valuable for use in immunoassay procedures in research and in the determination of proteins of clinical importance. In addition to the mature proteins (processed by natural post-synthetic reactions) the product proteins can comprise prohormone-type molecules which represent the precursor of normal circulating forms of hormones. The .sup.125 I-protein, -hormone, or -prohormone can be employed advantageously in diagnosis to provide marker compounds for chromatographic detection, immunoprecipitation, and serum clearance testing.

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