30S ribosomal protein S2; Belongs to the universal ribosomal protein uS2 family.

50S ribosomal protein L3; One of the primary rRNA binding proteins, it binds directly near the 3'-end of the 23S rRNA, where it nucleates assembly of the 50S subunit; Belongs to the universal ribosomal protein uL3 family.

30S ribosomal protein S4; One of the primary rRNA binding proteins, it binds directly to 16S rRNA where it nucleates assembly of the body of the 30S subunit.

50S ribosomal protein L2; One of the primary rRNA binding proteins. Required for association of the 30S and 50S subunits to form the 70S ribosome, for tRNA binding and peptide bond formation. It has been suggested to have peptidyltransferase activity; this is somewhat controversial. Makes several contacts with the 16S rRNA in the 70S ribosome. Belongs to the universal ribosomal protein uL2 family.

30S ribosomal protein S13; Located at the top of the head of the 30S subunit, it contacts several helices of the 16S rRNA. In the 70S ribosome it contacts the 23S rRNA (bridge B1a) and protein L5 of the 50S subunit (bridge B1b), connecting the 2 subunits; these bridges are implicated in subunit movement. Contacts the tRNAs in the A and P-sites. Belongs to the universal ribosomal protein uS13 family.

50S ribosomal protein L13; This protein is one of the early assembly proteins of the 50S ribosomal subunit, although it is not seen to bind rRNA by itself. It is important during the early stages of 50S assembly.

30S ribosomal protein S15; Forms an intersubunit bridge (bridge B4) with the 23S rRNA of the 50S subunit in the ribosome.

50S ribosomal protein L4; Forms part of the polypeptide exit tunnel.

30S ribosomal protein S3; Binds the lower part of the 30S subunit head. Binds mRNA in the 70S ribosome, positioning it for translation; Belongs to the universal ribosomal protein uS3 family.