Bhuta P, Kumar G, Chládek S
Biochim Biophys Acta. 1982 Feb 26;696(2):208-11. doi: 10.1016/0167-4781(82)90030-6.
The substrate specificity of the acceptor site of peptidyltransferase of Escherichia coli 70 S ribosomes was investigated in Ac-Phe-tRNA . poly(U) . 70 S ribosome (system A) and tRNC-A-Phe . poly(U) . C-A-C-C-A-Phe . 70 S ribosome (system B) systems by using C-C-A-Gly, C-C-A-Phe, C-A-Gly and C-A-Phe as analogs of the 3'-terminus of aminoacyl-tRNA. It was found that an addition of CP residue to C-A-Gly and C-APhe resulted in an increase of the acceptor activity in system A; the increase is more remarkable for C-A-Gly than for C-A-Phe, while the acceptor activities of C-C-A-Gly and C-C-A-Phe are roughly similar. On the other hand, dramatically increased binding affinities of C-C-A-Phe and C-C-A-Gly relative to C-A-Phe and C-A-Gly for the A site of peptidyltransferase were observed in system B using an inhibition assay; C-C-A-Phe binds much more strongly than C-C-A-Gly. The results indicate the important role of the third CP residue and the aminoacyl moiety of the 3'-terminus of aminoacyl-tRNA in the interaction with the acceptor site of peptidyltransferase, as well as the existence of cooperative effects between A and P sites of peptidyltransferase. These effects, depending on an occupancy of P site, may significant the specificity of the peptidyltransferase A site.
在Ac-Phe-tRNA·聚（U）·70S核糖体（系统A）和tRNC-A-Phe·聚（U）·C-A-C-C-A-Phe·70S核糖体（系统B）系统中，通过使用C-C-A-Gly、C-C-A-Phe、C-A-Gly和C-A-Phe作为氨酰基-tRNA 3'-末端类似物，研究了大肠杆菌70S核糖体肽基转移酶受体位点的底物特异性。发现向C-A-Gly和C-A-Phe添加CP残基会导致系统A中受体活性增加；C-A-Gly的增加比C-A-Phe更显著，而C-C-A-Gly和C-C-A-Phe的受体活性大致相似。另一方面，在系统B中使用抑制试验观察到，相对于C-A-Phe和C-A-Gly，C-C-A-Phe和C-C-A-Gly与肽基转移酶A位点的结合亲和力显著增加；C-C-A-Phe的结合比C-C-A-Gly强得多。结果表明，氨酰基-tRNA 3'-末端的第三个CP残基和氨酰基部分在与肽基转移酶受体位点的相互作用中起重要作用，以及肽基转移酶A和P位点之间存在协同效应。这些效应取决于P位点的占据情况，可能影响肽基转移酶A位点的特异性。
