(ORDO NEWS) — German biochemists have recreated a 2-billion-year-old bacterial enzyme that catalyzed chemical reactions in bacterial cells and compared it to its modern descendants, which are more efficient. The study made it possible to learn a lot about the evolution and properties of bacterial enzymes.
Scientists from the University of Leipzig (Germany) have reconstructed an ancient enzyme – tRNA-nucleotidyltransferase.
These proteins attach three nucleotides to transfer RNAs so that they can later supply amino acids for protein synthesis.
Using phylogenetic reconstructions, the researchers recreated a candidate for the role of the ancestral tRNA nucleotidyl transferase, which catalyzed reactions in bacterial cells about two billion years ago. The scientists then compared the properties of the resulting enzyme with its modern counterpart.
It turned out that both enzymes work with the same accuracy, but the reaction proceeds differently. A modern enzyme repeatedly interrupts its activity.
For decades, biochemists could not understand the evolutionary advantage of such a reaction. Only a comparison with an ancient enzyme made it possible to solve this riddle.
The reconstruction of the enzyme was a three-step process. First, the authors searched databases for modern tRNA nucleotidyl transferases to study their amino acid sequences, which the scientists then used to calculate what the ancestral sequence should have looked like.
The desired gene sequence encoding the ancient object was then introduced into bacterial cells that synthesized the desired protein.
Like organisms, enzymes are optimized through evolution. Enzyme catalysis usually proceeds faster and better when the protein binds its substrate tightly.
The redesigned ancestral enzyme does just that: it clings tightly to its substrate, the transfer RNA, and attaches three nucleotides to it.
Modern tRNA nucleotidyltransferases, on the contrary, work in stages, with pauses during which they release their substrate. However, they are much faster and more efficient than their predecessors.
The explanation lies in the phenomenon of the reverse reaction, in which already attached nucleotides are again removed by the enzyme.
Whereas the strong binding of the ancestral enzyme to the substrate resulted in subsequent elimination, the reverse reaction of modern enzymes is almost completely prevented by pauses, and this allows them to work more efficiently than their predecessors.
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