News from Carter lab
This study, “A genomic database furnishes minimal functional glycyl-tRNA synthetases homologous to other, designed class II urzymes”, now Online in Nucleic Acids Research journal with open access, was driven by Postdoctoral Researcher Sourav Kumar Patra, who joined in the lab of Prof. Charles W. Carter Jr. of Dept. of Biochemistry & Biophysics in July, 2022.
This was a collaborative effort between Charles W. Carter Jr., Peter R. Wills and Jordan Douglas. The study opens a new perspective from which we can now frame a substantially clearer set of questions about the origin of the genetic code. Each of the designed AARS urzymes, that Carter lab have characterized behaves remarkably consistently with the requirements for a redundant four-letter code. Unlike, previously studied urzymes which were all engineered for the purpose of testing the Rodin-Ohno hypothesis of bidirectional ancestry for Class I and II AARS were driven by hypothesis, but not by observations from natural sources like these GlyCA and GlyCA1-2.
Abstract: The hypothesis that conserved core catalytic sites could represent ancestral aminoacyl-tRNA synthetases (AARS) drove the design of functional TrpRS, LeuRS, and HisRS ‘urzymes’. We describe here new urzymes detected in the genomic record of the arctic fox, Vulpes lagopus. They are homologous to the α-subunit of bacterial heterotetrameric Class II glycyl-tRNA synthetase (GlyRS-B) enzymes. AlphaFold2 predicted that the N-terminal 81 amino acids would adopt a 3D structure nearly identical to our designed HisRS urzyme (HisCA1). We expressed and purified that N-terminal segment and the spliced open reading frame GlyCA1–2. Both exhibit robust single-turnover burst sizes and ATP consumption rates higher than those previously published for HisCA urzymes and comparable to those for LeuAC and TrpAC. GlyCA is more than twice as active in glycine activation by adenosine triphosphate as the full-length GlyRS-B α2 dimer. Michaelis–Menten rate constants for all three substrates reveal significant coupling between Exon2 and both substrates. GlyCA activation favours Class II amino acids that complement those favoured by HisCA and LeuAC. Structural features help explain these results. These minimalist GlyRS catalysts are thus homologous to previously described urzymes. Their properties reinforce the notion that urzymes may have the requisite catalytic activities to implement a reduced, ancestral genetic coding alphabet.
Publication Link: https://doi.org/10.1093/nar/gkae992
Carter lab previously designed the urzymes but this time we found it from natural source. Which Supports our AI driven study of Urzyme model throughout past many years.