Protein Domain : Ribosomal protein L12/P1/P2 family IPR027534

Type	Family
Description	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 [ , , ]. 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 []. In lower eukaryotes, P1 and P2 are further subdivided into P1A, P1B, P2A, and P2B, which form P1A/P2B and P1B/P2A heterodimers []. Some plants have a third P-protein, called P3, which is not homologous to P1 and P 2 [].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 [ ].Archaeal L12 is functionally equivalent to L7/L12 in bacteria and the P1 and P2 proteins in eukaryotes. L12 is homologous to P1 and P2 but is not homologous to bacterial L7/L12. It is located in the L12 stalk, with proteins L10, L11, and 23S rRNA. In several mesophilic and thermophilic archaeal species, the binding of 23S rRNA to protein L11 and to the L10/L12p pentameric complex was found to be temperature-dependent and cooperative [ ].This entry includes eukaryotic 60S acidic ribosomal protein P1/P2 , as well as archaeal 50S ribosomal protein L12. These proteins play an important role in the elongation step of protein synthesis [ , ].
Short Name	Ribosomal_L12/P1/P2