Peer review

The classical Osborne-Mendel extraction procedure for corn endosperm protein was modified to extract additional protein by a solvent containing 55% 2-propanol and 0.6% 2-mercaptoethanol. The new fraction is designated zein-2, since it has an amino acid composition somewhat similar to zein, but with higher levels of glycine, methionine, histidine, and proline, and lower levels of aspartic acid, leucine, and isoleucine. Zein-2 was previously recovered as a part of the glutelin fraction. Zein-1 and zein-2 , as well as glutelin, were heterogeneous by polyacrylamide gel electrophoresis. However. these three protein fractions had characteristic amino acid compositions which were constant for normal, opaque-2, and floury-2 endosperms. The two mutations which increase the lysine content of the endosperm act by changing the proportions of proteins which contain different levels of lysine.

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