Can't you translate the protein? It could be that the amino acid sequence is destroying the ribosome

background Protein is a three position structure composed of polypeptide chain The amino acid sequence of polypeptide chain is written by DNA code The process of preparing polypeptide chain takes place in ribosome They are called protein synthesis machine According to the genetic code, messenger RNA from DNA copy sequence polymerizes amino acid molecules one by one until the end of the whole chain is separated from the ribosome   The process by which ribosomes synthesize proteins is called translation, so all proteins in an organism are produced through translation In the past, it was thought that in the process of translation, a nascent chain was produced continuously Until recently, the research team of Hideki Taguchi of Tokyo technology and koraiki Ito of Kyoto Sangyo University found that the translation speed was actually very fluctuant, and some special amino acid sequences of new chains acting on ribosomes would slow down the translation speed   Overview of research results A group of proteins with 10 special amino acid sequences (aspartic acid and glutamic acid) or acid amino acid and proline alternately linked in the sequences were translated by recombinant E.coli cell-free translation system When ribosomes are translated into these special sequences, there is an obvious pause The result of being affected by the new chains that contain these sequences is that the ribosome becomes unstable The researchers named the event "internal ribosome destabilization (IRD)."   It directly causes ribosomes to split into subunits, large and small (see Figure) Ribosomes, once thought to be the headquarters of all amino acid sequences, have now been shown to be able to be overthrown by the new chains they produce This shows that there is a potential risk of failure in the process of translation Proteins rich in the sequence that triggers IRD are not fully synthesized At first glance, this seems to be a defect in ribosome But, think about it carefully, is the existence of IRD meaningful to life?
The researchers found that there are also mechanisms in organisms that counteract IRD So they analyzed cell proteomics (all protein expression) using mutated E.coli, which lacks this mechanism (a little bit of instability tends to produce IRD) As a result, the number of many proteins has changed Among them, the most special one is mgta membrane protein, which is responsible for transporting magnesium ions into cells The mgta expression of mutant E.coli is more than 10 times higher than that of wild type   Why is the high incidence of IRD leading to the high expression of mgta protein in cells?
The researchers found that the mgtl gene, which controls mgta expression, also has an IRD sequence Escherichia coli perceives the IRD phenomenon through a special mechanism of mgtL sequence, and then regulates MgtA expression to respond to the change of intracellular magnesium concentration Magnesium ion has many important functions, especially for ribosome stabilization The results of this study show that when E.coli perceives that magnesium ions are scarce in the environment, it will use IRD of mgtl to induce mgta expression in large quantities to obtain a way to maintain the intracellular magnesium concentration In other words, living organisms have a regulatory mechanism that uses the IRD phenomenon to monitor the intracellular environment (see Figure) Future research This study shows that in addition to proteins with three-dimensional structure, amino acid sequences can also affect ribosome stability or even terminate translation Previously, early termination of translation has not been considered an important process in life science, and the Taguchi team's achievements are the expansion of this field, which is likely to lead to new tool protein production or biopharmaceutical development.