Two different species of messenger RNAs specify synthesis of M1 and M2 pyruvate kinase subunits

A study was performed to determine whether M₁ and M₂ pyruvate kinases were synthesized under the direction of one or two messenger RNAs. We compared M₁ and M₂ pyruvate kinases purified from fresh tissues with those neosynthesized under the direction of messenger RNAs from tissues synthesizing either M₁ or M₂. RNA was isolated from rat muscle, lung, spleen and kidney by ethanol precipitation in 7 M guanidium chloride, translated in rabbit reticulocyte system and newly-synthesized pyruvate kinase subunits were purified by microimmunoaffinity chromatography. Pyruvate kinase from fresh muscle and spleen was purified in one step by a similar process. Muscle and spleen RNA directed the synthesis of M subunits with molecular weights of approx. 61000 and 62000, respectively, the same as those of the corresponding fresh tissue monomers. In addition, peptide maps obtained by partial digestion of neosynthesized M₁ and M₂ with V₈ protease from Staphylococcus aureus confirmed that these polypeptides were clearly different.