Equipe de Photobiologie Moléculaire, UPMC Université Paris 06, 2 Place Jussieu, 75252 Paris Cedex 05, France.
Chembiochem. 2012 Aug 13;13(12):1791-7. doi: 10.1002/cbic.201200208.
Previously we have shown that the CCA end of a P-tRNA can be crosslinked with the RPL36AL protein of the large subunit of mammalian ribosomes; it belongs to the L44e protein family present in all eukaryotic and archaeal ribosomes. Here we confirm and extend this finding and demonstrate that: 1) this crosslink is specific for a tRNA at the P/E hybrid site, as a tRNA in all other tRNA positions of pre-translocational ribosomes could not be crosslinked with a ribosomal protein, 2) the crosslink was formed most efficiently with C74 and C75 of P/E-tRNA, but could also connect the ultimate A of this tRNA with Lys53 of protein RPL36AL, 3) this protein contains seven monomethylated residues (three lysyl and three arginyl residues, as well as glutaminyl residue 51), 4) Q51 is part of a conserved GGQ motif in the L44e proteins in eukaryotic 80S ribosomes that is identical to the universally conserved motif of release factors implicated in promoting peptidyl-tRNA hydrolysis, and 5) the large number of modifications, in which some of the residues were methylated to about 50 %, might indicate that protein RPL36AL is a preferential target for regulation.
此前我们已经表明，P-tRNA 的 CCA 末端可以与哺乳动物核糖体大亚基的 RPL36AL 蛋白发生交联；它属于存在于所有真核生物和古菌核糖体中的 L44e 蛋白家族。在这里，我们证实并扩展了这一发现，并证明：1）这种交联是 P/E 杂交位点上 tRNA 的特异性，因为处于前移位核糖体中所有其他 tRNA 位置的 tRNA 不能与核糖体蛋白发生交联，2）交联最有效地形成于 P/E-tRNA 的 C74 和 C75，但也可以将该 tRNA 的最终 A 与蛋白 RPL36AL 的 Lys53 连接，3）该蛋白含有七个单甲基化残基（三个赖氨酸和三个精氨酸残基，以及谷氨酰残基 51），4）Q51 是真核 80S 核糖体中 L44e 蛋白中保守的 GGQ 基序的一部分，与普遍保守的参与促进肽酰-tRNA 水解的释放因子的基序相同，5）大量的修饰，其中一些残基被甲基化约 50%，可能表明蛋白 RPL36AL 是调控的优先目标。
