Ribosomal proteins S3, S6, S8 and S10 of Escherichia coli localized on the external surface of the small subunit by immune electron microscopy

Abstract

The three-dimensional locations of Escherichia coli ribosomal proteins S3, 86, S8 and S10 on the surface of the small subunit were determined by immune electron microscopy. All four proteins are located on the “external surface” of the small subunit; i.e. on the side of the subunit in contact with the cytosol in the 70 S ribosome. Proteins S3, S6, S8 and S10 map at single sites, although the S3 site is extended approximately 40Å along the long axis of the subunit. S8 is located near the base of the cleft separating the platform from the upper one-third or head; protein S10 is located in the head, near the site previously mapped for S14; S3 extends from the level of the constriction to near the top of the head in the vicinity of S10; and S6 is located on the platform of the small subunit near the site previously mapped for S11. The locations of these proteins correlate well with other information on their spatial relationships obtained from assembly interactions, neutron diffraction, crosslinking and protein associations.