InterPro domain: IPR044076

Eukaryotic P1 and P2 are functionally equivalent to the bacterial protein L7/L12, but are not homologous to L7/L12. P2 is located in the L12 stalk, with proteins P1, P0, L11, and 28S rRNA. P1 and P2 are the only proteins in the ribosome to occur as multimers, always appearing as sets of heterodimers. Eukaryotes have four copies (two heterodimers), while most archaeal species contain six copies of L12p (three homodimers). Bacteria may have four or six copies of L7/L12 (two or three homodimers) depending on the species [ 1 , 2 , 3 ]. Experiments using S. cerevisiae P1 and P2 indicate that P1 proteins are positioned more internally with limited reactivity in the C-terminal domains, while P2 proteins seem to be more externally located and are more likely to interact with other cellular components [ 4 ]. In lower eukaryotes, P1 and P2 are further subdivided into P1A, P1B, P2A, and P2B, which form P1A/P2B and P1B/P2A heterodimers [ 5 ]. Some plants have a third P-protein, called P3, which is not homologous to P1 and P 2 [ 6 ].

In humans, P1 and P2 are strongly autoimmunogenic. They play a significant role in the etiology and pathogenesis of systemic lupus erythema (SLE). In addition, the ribosome-inactivating protein trichosanthin (TCS) interacts with human P0, P1, and P2, with its primary binding site in the C-terminal region of P2. TCS inactivates the ribosome by depurinating a specific adenine in the sarcin-ricin loop of 28S rRNA [ 7 ].

This entry represents the eukaryotic large ribosomal protein P2.

1. Proteins P1, P2, and P0, components of the eukaryotic ribosome stalk. New structural and functional aspects. Biochem. Cell Biol. 73, 959-68
2. Structure and function of the acidic ribosomal stalk proteins. Curr. Protein Pept. Sci. 3, 93-106
3. Structural characterization of the ribosomal P1A-P2B protein dimer by small-angle X-ray scattering and NMR spectroscopy. Biochemistry 46, 1988-98
4. Different roles of P1 and P2 Saccharomyces cerevisiae ribosomal stalk proteins revealed by cross-linking. Mol. Microbiol. 62, 1191-202
5. Oligomerization properties of the acidic ribosomal P-proteins from Saccharomyces cerevisiae: effect of P1A protein phosphorylation on the formation of the P1A-P2B hetero-complex. Biochim. Biophys. Acta 1499, 63-73
6. Ribosomal P3 protein AtP3B of Arabidopsis acts as both protein and RNA chaperone to increase tolerance of heat and cold stresses. Plant Cell Environ. 39, 1631-42
7. Interaction between trichosanthin, a ribosome-inactivating protein, and the ribosomal stalk protein P2 by chemical shift perturbation and mutagenesis analyses. Nucleic Acids Res. 35, 1660-72