Abstract

Post-translational hydroxylation occurs in three mammalian ribosomal proteins, uS12, uL2, and uL15, which are located in the small (S) and large (L) subunits of the ribosome near the most important decoding and peptidyltransferase functional centers. We have used cell cultures, which produce protein uL15 labeled with the 3xFLAG epitope at the C-terminus (uL15^3xFLAG) or mutant forms of uL15^3xFLAG that contain His39Ala, His39Thr, or His40Ala substitutions, to examine the role of hydroxylated His39 of uL15 in maintaining the translational activity of ribosomes. It has been found that exogenous uL15^3xFLAG is able to functionally replace endogenous uL15 in HEK293 cells transfected with an appropriate DNA construct. However, the translational activity of ribosomes decreases by about 35% in cells that produce the above mutant forms of uL15^3xFLAG compared with that in cells that produce nonmutated uL15^3xFLAG. Analysis of the structural model of the human ribosome has allowed us to assume that the hydroxyl group in His39 is involved in the local stabilization of the ribosome structure through the formation of a hydrogen bond between this group and the nitrogen atom of the His40 imidazole ring. Given that His39 is located near the E site of the ribosome, we believe that this stabilization of the ribosome structure ensures the maintenance of its translational activity.

中文翻译：

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用Ala或Thr取代核糖体蛋白uL15中的羟化His39损害人核糖体的翻译活性

摘要

翻译后羟基化发生在三种哺乳动物核糖体蛋白，即uS12，uL2和uL15中，它们位于核糖体最重要的解码和肽基转移酶功能中心附近的小（S）和大（L）亚基中。我们已经使用的细胞培养物，其产生蛋白UL15标记具有在C末端（UL15的3XFLAG表位^3XFLAG）或UL15的突变体形式^3XFLAG包含His39Ala，His39Thr，或His40Ala取代，以检查在UL15的羟基化His39的作用维持核糖体的翻译活性。已经发现外源的uL15 ^3xFLAG能够在用适当的DNA构建体转染的HEK293细胞中功能性替代内源性uL15。然而，与产生非突变的uL15 ^3xFLAG的细胞相比，在产生上述突变形式的uL15 ^3xFLAG的细胞中核糖体的翻译活性降低了约35％。对人核糖体结构模型的分析使我们可以假设，His39中的羟基通过在该基团与His40咪唑环的氮原子之间形成氢键而参与了核糖体结构的局部稳定化。鉴于His39位于核糖体E位点附近，我们相信核糖体结构的这种稳定作用可确保维持其翻译活性。