Day 209 has 49 protein-coding genes (browser view), including IARS (isoleucyl-tRNA synthetase).
IARS is one of the 20 aminoacyl tRNA synthetase enzymes, which “charge” tRNAs with the appropriate amino acids to prepare them for building proteins on the translating ribosome. These enzymes are ancient and shared across all of life.
From Woese et al. (2000):
The aminoacyl-tRNA synthetases (AARSs) have long fascinated biologists. They are the linchpin of translation, the link between the worlds of protein and nucleic acid. Their structures and functions, which have both practical and basic significance, are deserving of and have received much attention. However, it is not only the structure-function aspect of these enzymes that has captured the biologist’s imagination; it is also the possibility that they could tell us the secrets of the genetic code. To understand these enzymes in standard molecular terms is to add one more piece, a most important one, to the puzzle of what the cell is, how it works. But to understand them in evolutionary terms is to ask what the cell is in a deeper sense, how it evolved, how life came to be—the biologist’s ultimate question.
Click here to see all 8649670 letters of Day 209 with IARS underlined.