Human ribosomal P1-P2 heterodimer represents an optimal docking site for ricin A chain with a prominent role for P1 C-terminus

• Published in: Scientific reports Vol. 7; no. 1; pp. 5608 - 11
• Main Authors: Grela, Przemysław, Li, Xiao-Ping, Horbowicz, Patrycja, Dźwierzyńska, Monika, Tchórzewski, Marek, Tumer, Nilgun E.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 17.07.2017; Nature Publishing Group; Nature Portfolio
• Subjects: 631/45; 631/45/612/1249; 82/103; 82/58; 82/83; Affinity; C-Terminus; Calorimetry; Humanities and Social Sciences; Interferometry; multidisciplinary; p1 Protein; Proteins; Ricin; Science; Science (multidisciplinary); Surface plasmon resonance; Titration
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-017-05675-5

The eukaryotic P-stalk contains two P1-P2 protein dimers with a conserved C- terminal domain (CTD) critical for the interaction with external factors. To understand the role of the individual CTD of human P1/P2 proteins, we examined the interaction of reconstituted human P-protein complexes and C-terminally truncated forms with ricin A chain (RTA), which binds to the stalk to depurinate the sarcin/ricin loop (SRL). The interaction between P-protein complexes and RTA was examined by surface plasmon resonance, isothermal titration calorimetry, microscale thermophoresis and bio-layer interferometry. The P1-P2 heterodimer missing a CTD on P2 was able to bind RTA. In contrast, the P1-P2 heterodimer missing the CTD of P1 protein displayed almost no binding toward RTA. Very low interaction was detected between RTA and the non-truncated P2-P2 homodimer, suggesting that the structural architecture of the P1-P2 heterodimer is critical for binding RTA. The reconstituted pentameric human stalk complex had higher affinity for RTA than the P1-P2 dimer. Deletion of P1 CTD, but not P2 CTD reduced the affinity of the pentamer for RTA. These results highlight the importance of the heterodimeric organization of P1-P2 in the human stalk pentamer and functional non-equivalence of the individual P-protein CTDs in the interaction with RTA.