Isolation, properties, and structure of fraction I protein from Avena sativa L.

1. A method is described for the extraction and purification of Fraction I protein from Avena sativa L. leaves. 2. The protein possesses ribulose diphosphate carboxylase activity. Chromatography on gels of Sephadex G-200 separates phosphoribulokinase and ribose phosphate isomerase from the carboxylase. 3. The S°20w was calculated to be 18.2, the Stokes radius (determined by gel filtration on a cabibrated column) 74 Å, the molecular weight 5.7×10(5), and the frictional ratio 1.35. 4. An amino acid analysis is presented. 5. Electron microscope observations of negatively-stained Avena Fraction I protein molecules are compatible with the suggestion that they consist of 24 protomers disposed on the surface of an octahedral shell with 4:3:2 symmetry, and of diameter approximately 105 Å.