Inside cells, ribosomes read the DNA that carries genetic information and link tens to thousands of amino acids of 20 types in a specific order to build proteins. It has recently come to light that certain amino acid sequences are difficult for ribosomes to synthesize. These are called "translation-impeding sequences." Because such sequences halt protein synthesis, they are inherently disadvantageous to organisms and understanding how their existence has shaped biological evolution is extremely important.
A research group led by Specially Appointed Assistant Professor Keigo Fujiwara from the National Institute of Genetics and Professor Shinobu Chiba from Kyoto Sangyo University identified a pattern of translation-impeding sequences shared broadly across bacteria and further revealed that a unique group of proteins actively makes use of such sequences. The group first used systematic mutational analysis to establish that amino acid sequences containing arginine-glycine-proline-proline (RGPP) or arginine-alanine-proline-proline (RAPP) are prone to becoming translation-impeding sequences. They then analyzed genetic information covering the entire bacterial kingdom and found that the RGPP sequence has the lowest occurrence frequency of any such sequence across all bacteria. The group further focused on actinobacteria, which have a particularly high number of proteins carrying RAPP or RGPP sequences near their carboxy terminus. Their bioinformatic analysis showed that these proteins appear to have a previously unknown physiological function—they are likely involved in monitoring and adapting to the environment inside and outside the cell.
These findings provide fundamental insights into the evolution of genetic information, gene expression, and the molecular mechanisms of translation. The results are also expected to be useful in "biomanufacturing," which uses bacteria and microorganisms to produce valuable compounds, as well as the development of antibiotics.
(Article: Masanori Nakajo)
