Primary structure of rat ribosomal protein S2. A ribosomal protein with arginine-glycine tandem repeats and RGGF motifs that are associated with nucleolar localization and binding to ribonucleic acids.

The amino acid sequence of the rat 40 S ribosomal subunit protein S2 was deduced from the sequence of nucleotides in two recombinant cDNAs and confirmed from the amino acid sequence of a cyanogen bromide peptide obtained from the protein. Ribosomal protein S2 has 293 amino acids and has a molecular weight of 31,211. Hybridization of the cDNA to digests of nuclear DNA suggests that there are 23-28 copies of the S2 gene. The mRNA for the protein is about 1,000 nucleotides in length. The highly conserved repetitive mammalian gene family designated LLRep3, but not identified before, encodes ribosomal protein S2. Rat S2 is related to Saccharomyces cerevisiae S4, Methanococcus vannielii S5, Escherichia coli S5, and other members of the prokaryotic S5 family. S. cerevisiae S4 and E. coli S5 are involved in the binding of aminoacyl-tRNA to ribosomes and in conditioning the fidelity of translation; it is plausible to assume that rat S2 serves similar functions. The NH2-terminal region of S2 is rich in arginine-glycine repeats including eight that occur in tandem and has two consecutive copies of the motif RGGF; these sequences have been associated with nucleolar localization and binding to RNA.