Electron microscopic investigations on the location of rat liver ribosomal proteins S3a, S5, S6, S7 and S9 by means of antibody labeling.

The location of ribosomal proteins S3a, S5, S6, S7 and S9 on the surface of 40S subunits of rat liver ribosomes has been determined by means of antibody labeling and electron microscopy. Multiple antigenic determinants could be detected for proteins S3a, S6 and S7, whereas protein S9 shows only one and protein S5 two closely neighboured antigenic determinants. Antigenic determinants of proteins S3a, S6 and S7 have been mapped in the head and the body region of the 40S subunits. Protein S5 could be localized in the head and protein S9 in the body of the 40S subunits. These findings are discussed with regard to the location of functional sites on the 40S ribosomal subunit.