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Importance of Ribosome Purity in Ribosomal Serology. Hacène Bouzar, Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331; Larry W. Moore(2), and Henry W. Schaup(3). (2)Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331; (3)Department of Biochemistry and Biophysics, Oregon State University, Corvallis 97331. Phytopathology 76:1323-1325. Accepted for publication 9 June 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-1323.

Antisera made from unwashed preparations of 50 S ribosomal subunits of Agrobacterium gave reproducible immuno-precipitation patterns when reacted with ammonium sulfate-washed ribosomes, but the patterns were not always reproducible when reacted with unwashed ribosomes. We suspected that this lack of reproducibility was due to a nonribosomal antigen associated with unwashed ribosomes. The association of this antigenic contaminant with the unwashed ribosomes was demonstrated when antiserum to heat-stable antigens of whole cells and antiserum to unwashed ribosomes reacted with both heat-stable antigens of whole cells and unwashed ribosomes to produce confluent precipitin bands. This contaminant was also associated with unwashed 50 S subunits. The contaminant was removed by ammonium sulfate fractionation and the subsequent sedimentation of the ribosomes in the presence of 0.6 M ammonium sulfate. The contaminant was not associated with either ammonium sulfate-washed ribosomes nor the proteins extracted from the highly purified 50 S subunits. Therefore, nonspecific binding of a somatic antigen to unwashed ribosomal particles appears to offer the most probable explanation for the additional antigenic response.