Now, researchers at the University of Michigan and the Academy of Sciences of the Czech Republic have uncovered two previously unknown roles for water in RNA enzymes, molecules which themselves play critical roles in living cells and show promising medical applications.
The researchers' findings will be published online in the Proceedings of the National Academy of Sciences (PNAS) this week.
RNA enzymes, also known as ribozymes, accelerate chemical reactions inside cells, just as their better-known protein counterparts do. And just as a protein enzyme is not a static structure, a ribozyme also changes shape, cycling back and forth between active and inactive forms (called conformations).
In earlier work, a team led by U-M's Nils Walter, associate professor of chemistry, found that modifications made anywhere on the ribozyme molecule---even far from the site where the chemical reaction occurs---affect the rates at which the enzyme changes conformation and catalyzes the reaction. Something similar had been seen in protein enzymes, but never before in RNA enzymes.
The earlier finding, published in PNAS two years ago, suggested that information about changes in distant parts of the ribozyme travels through some sort of network to the core of the molecule, where chemical reactions take place. The latest work shows that water molecules trapped inside the ribozyme's core are essential components of that network.
The network acts like a jostling crowd at a cocktail party, where hydrogen bonds---weak, electrostatic attractions between molecules or parts of molecules---take the place of handshakes. Water molecules trapped in ribozymes can form hydrogen bonds with other water molecules or with parts of the ribozyme molecule.
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Source:University of Michigan