Ribosomal Protein

What Are Ribosomal Proteins

Ribosomal proteins, also known as r-proteins or rProtein, are proteins involved in the process of ribosome biosynthesis. They synthesize proteins by translating information from RNA. The main function of ribosomal proteins is to cooperate with RNA to form ribosomal subunits and large ribosomes, thus facilitating the synthesis of polypeptide chains. They are capable of linking amino acid sequences through specific chemical reactions to form complete polypeptide chains. Ribosomal proteins are highly complex in structure and function and play a key role in the fundamental processes of life. Some ribosomal protein genes are highly expressed in tumor tissues such as gastric cancer, colorectal cancer and hepatocellular carcinoma, and the in-depth study of ribosomal protein gene high expression in tumor tissues can help to elucidate the mechanism of tumor occurrence and progression.

Ribosomal proteins of Escherichia coli

Current knowledge of ribosomal proteins comes mainly from studies on the ribosome of Escherichia coli (E. coli). The small ribosomal subunit of E. coli cells contains about 22 proteins (numbered S1 to S22) and its large ribosomal subunit contains about 34 proteins (numbered L1 to L36). These proteins are immunologically independent proteins, with only L7 and L12 exhibiting cross-reactivity with each other. All of these ribosomal proteins except S6, L7 and L12 are basic proteins. In addition, all ribosomal proteins differ from each other, except for the three specific groups listed below:

• S20 and L26 were confirmed to be the same protein, and it is the only protein that appears in both large and small subunits.
• L7 and L12 are the N-terminal acetylated version and the internally methylated version of the peptide chain of the same protein, respectively.
• L8 is a complex of L7 (or L12) and L10.

Fig. 1 Interaction between L6 protein and the 50S ribosomal subunit.¹

The Evolutionary Relationship of Ribosomal Proteins

As the number of sequenced genomes continues to grow, the ribosomal protein sequence database is also expanding rapidly. Sequence comparisons show that more than 50% of eubacterial ribosomal proteins have homologous proteins in chloroplasts, archaea and eukaryotes. If structural information is found, the prediction of conserved proteins will increase, as protein differences are often beyond the scope of sequence comparisons. Identifying sequence motifs or mapping structure to function may extend the fraction of proteins conserved between different domains. In addition, structural studies of ribosomal proteins suggest that several different ribosomal proteins may derive from a common origin. Structural studies have also revealed relationships between ribosomal proteins and other protein functions. Additional sequence and structural data could determine whether this is by a common evolutionary origin.

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Reference

1. Gulati, Megha, et al. "Functional interaction between ribosomal protein L6 and RbgA during ribosome assembly." PLoS Genetics 10.10 (2014): e1004694.