Nascent polypeptides can modulate the polypeptide elongation speed on the ribosome. Here, we show that nascent chains can even destabilize the translating Escherichia coli ribosome from within. This phenomenon, termed intrinsic ribosome destabilization (IRD), occurs in response to a special amino acid sequence of the nascent chain, without involving the release or the recycling factors. Typically, a consecutive array of acidic residues and those intermitted by alternating prolines induce IRD. The ribosomal protein bL31, which bridges the two subunits, counteracts IRD, such that only strong destabilizing sequences abort translation in living cells. We found that MgtL, the leader peptide of a Mg²⁺ transporter (MgtA), contains a translation-aborting sequence, which sensitizes the ribosome to a decline in Mg²⁺ concentration and thereby triggers the MgtA-upregulating genetic scheme. Translation proceeds at an inherent risk of ribosomal destabilization, and nascent chain-ribosome complexes can function as a Mg²⁺ sensor by harnessing IRD.

新生多肽可以调节核糖体上多肽的延伸速度。在这里，我们显示新生链甚至可以从内部破坏翻译大肠杆菌的核糖体。这种现象被称为固有核糖体失稳（IRD），是对新生链的特殊氨基酸序列的响应而发生的，而不涉及释放或循环利用因素。通常，连续的酸性残基阵列和交替的脯氨酸间断的酸性残基会诱导IRD。桥接两个亚基的核糖体蛋白bL31与IRD相互作用，因此只有强的去稳定序列才能使活细胞中的翻译中止。我们发现MgtL是Mg ²⁺的前导肽转运蛋白（MgtA）包含一个翻译中止序列，该序列使核糖体对Mg ²⁺浓度的下降敏感，从而触发了MgtA上调基因方案。进行翻译存在核糖体不稳定的内在风险，新生的链-核糖体复合物可通过利用IRD充当Mg ²⁺传感器。