Cycloheximide Resistant Incorporation of Amino Acids into a Polypeptide of the Cytochronic Oxidase of Neurospora crassa.

Radioactive leucine was incorporated by Neurospora crassa mitochondria in vivo in the presence of cycloheximide. When the membrane protein of these mitochondria was chromatographically separated on oleyl polymethacrylic acid resin, a number of fractions were obtained which differ with respect to their contents of radioactivity and cytochromes. The highest specific radioactivity was found in the fraction containing cytochrome aa3. This fraction proved to be a pure and enzymatically active cytochrome oxidase. Its ratio of absorbance at, 280 nm (ox)/ 443 nm (red.) was 2.1. By means of sodium dodecylsuffate gel-electrophoresis, this enzyme was separated into five polypeptides with molecular weights of 30000, 20000, 13000, 10000, and 8000. Only the polypeptide with the molecular weight 20000 displayed a high specific radioactivity. [ABSTRACT FROM AUTHOR]