Analysis of the protein-protein interactions between the human acidic ribosomal P-proteins: evaluation by the two hybrid system.

The surface acidic ribosomal proteins (P-proteins), together with ribosomal core protein P0 form a multimeric lateral protuberance on the 60 S ribosomal subunit. This structure, also called stalk, is important for efficient translational activity of the ribosome. In order to shed more light on the function of these proteins, we are the first to have precisely analyzed mutual interactions among human P-proteins, employing the two hybrid system. The human acidic ribosomal P-proteins, (P1 or P2,) were fused to the GAL4 binding domain (BD) as well as the activation domain (AD), and analyzed in yeast cells. It is concluded that the heterodimeric complex of the P1/P2 proteins is formed preferentially. Formation of homodimers (P1/P1 and P2/P2) can also be observed, though with much less efficiency. Regarding that, we propose to describe the double heterodimeric complex as a protein configuration which forms the 60 S ribosomal stalk: P0-(P1/P2)(2). Additionally, mutual interactions among human and yeast P-proteins were analyzed. Heterodimer formation could be observed between human P2 and yeast P1 proteins.