Lentzen G, Dobberstein B, Wintermeyer W
Institut für Molekularbiologie, Universität Witten/Herdecke, Germany.
FEBS Lett. 1994 Jul 18;348(3):233-8. doi: 10.1016/0014-5793(94)00599-0.
E. coli P48 protein is homologous to the SRP54 component of the eukaryotic signal recognition particle. In vivo, P48 is associated with 4.5S RNA which shares a homology with eukaryotic SRP RNA. To study the interaction between P48 and 4.5S RNA in vitro, we used 4.5S RNA with fluorescein coupled to the 3'-terminal ribose. Upon binding of P48, the fluorescent 4.5S RNA shows a substantial decrease in fluorescence. Fluorescence quenching as well as anisotropy measurements reveal that the effect is not due to a direct interaction of P48 with the dye. This suggests that the binding of P48 induces a conformational change in 4.5S RNA which affects the structure at the 3' end of the RNA. From equilibrium titrations with fluorescent 4.5S RNA, a dissociation constant of 0.15 microns is obtained for the RNA.protein complex. The formation of the complex is not affected by GTP binding to or hydrolysis by P48.
大肠杆菌P48蛋白与真核信号识别颗粒的SRP54组分同源。在体内，P48与4.5S RNA相关联，4.5S RNA与真核SRP RNA具有同源性。为了在体外研究P48与4.5S RNA之间的相互作用，我们使用了3'-末端核糖偶联有荧光素的4.5S RNA。P48结合后，荧光4.5S RNA的荧光显著降低。荧光猝灭以及各向异性测量表明，这种效应不是由于P48与染料的直接相互作用。这表明P48的结合诱导了4.5S RNA的构象变化，从而影响了RNA 3'端的结构。通过用荧光4.5S RNA进行平衡滴定，得到RNA-蛋白质复合物的解离常数为0.15微米。复合物的形成不受GTP与P48结合或P48水解的影响。
