Ribosomal protein P1, P2, and L12p. Ribosomal proteins P1 and P2 are the eukaryotic proteins that are functionally equivalent to bacterial L7/L12. L12p is the archaeal homolog. Unlike other ribosomal proteins, the archaeal L12p and eukaryotic P1 and P2 do not share sequence similarity with their bacterial counterparts. They are part of the ribosomal stalk (called the L7/L12 stalk in bacteria), along with 28S rRNA and the proteins L11 and P0 in eukaryotes (23S rRNA, L11, and L10e in archaea). In bacterial ribosomes, L7/L12 homodimers bind the extended C-terminal helix of L10 to anchor the L7/L12 molecules to the ribosome. Eukaryotic P1/P2 heterodimers and archaeal L12p homodimers are believed to bind the L10 equivalent proteins, eukaryotic P0 and archaeal L10e, in a similar fashion. P1 and P2 (L12p, L7/L12) are the only proteins in the ribosome to occur as multimers, always appearing as sets of dimers. Recent data indicate that most archaeal species contain six copies of L12p (three homodimers), while eukaryotes have two copies each of P1 and P2 (two heterodimers). Bacteria may have four or six copies (two or three homodimers), depending on the species. As in bacteria, the stalk is crucial for binding of initiation, elongation, and release factors in eukaryotes and archaea.

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                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 47524167   6 ELACIYSALILHDDEVTVTA-------------------------LANVNIGSLICNVGAGGPAPAAGAAPAGGPAPSTA 60
Cdd:cd05831   1 ELACTYAALILHDDGIEITAdninallkaagvnvepywpglfakaLEGKDIKDLLSNVGGGGGGAAPAAAAAAAAAAAAE 80

                        90       100
                ....*....|....*....|....*...
gi 47524167  61 AAPAEEKKVEAKKEeseesDDDMGFGLF 88
Cdd:cd05831  81 AKKEEKKEEEEEES-----DDDMGFGLF 103

Ribosomal protein P1. This subfamily represents the eukaryotic large ribosomal protein P1. Eukaryotic P1 and P2 are functionally equivalent to the bacterial protein L7/L12, but are not homologous to L7/L12. P1 is located in the L12 stalk, with proteins P2, 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. Recent data indicate that eukaryotes have four copies (two heterodimers), while most archaeal species contain six copies of L12p (three homodimers) and bacteria may have four or six copies (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 plant species have a third P-protein, called P3, which is not homologous to P1 and P2. 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 located in the C-terminal region of P2. TCS inactivates the ribosome by depurinating a specific adenine in the sarcin-ricin loop of 28S rRNA.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 47524167   6 ELACIYSALILHDDEVTVTA-------------------------LANVNIGSLICNVGAGGPAPAAGAAPAGGPAPSTA 60
Cdd:cd05831   1 ELACTYAALILHDDGIEITAdninallkaagvnvepywpglfakaLEGKDIKDLLSNVGGGGGGAAPAAAAAAAAAAAAE 80

                        90       100
                ....*....|....*....|....*...
gi 47524167  61 AAPAEEKKVEAKKEeseesDDDMGFGLF 88
Cdd:cd05831  81 AKKEEKKEEEEEES-----DDDMGFGLF 103

Ribosomal protein P1. This subfamily represents the eukaryotic large ribosomal protein P1. Eukaryotic P1 and P2 are functionally equivalent to the bacterial protein L7/L12, but are not homologous to L7/L12. P1 is located in the L12 stalk, with proteins P2, 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. Recent data indicate that eukaryotes have four copies (two heterodimers), while most archaeal species contain six copies of L12p (three homodimers) and bacteria may have four or six copies (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 plant species have a third P-protein, called P3, which is not homologous to P1 and P2. 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 located in the C-terminal region of P2. TCS inactivates the ribosome by depurinating a specific adenine in the sarcin-ricin loop of 28S rRNA.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 47524167   6 ELACIYSALILHDDEVTVTA-------------------------LANVNIGSLICNVGAGGPAPAAGAAPAGGPAPSTA 60
Cdd:cd05831   1 ELACTYAALILHDDGIEITAdninallkaagvnvepywpglfakaLEGKDIKDLLSNVGGGGGGAAPAAAAAAAAAAAAE 80

                        90       100
                ....*....|....*....|....*...
gi 47524167  61 AAPAEEKKVEAKKEeseesDDDMGFGLF 88
Cdd:cd05831  81 AKKEEKKEEEEEES-----DDDMGFGLF 103