A Potential Answer To Why Life Needs Water

A ribbon model of molecules of protein p53 binding to a strand of DNA. ibreakstock/shutterstock

Water is life. Wherever we look on this planet, biological processes require water, but exactly what role water plays has remained unclear. Until now.

A group of scientists from Ohio State University think they have finally cracked the mystery. Water plays a crucial role in the formation of proteins, which are just long chains of amino acids that are folded in a certain way. But according to the study, they can’t fold themselves without water.

“For a long time, scientists have been trying to figure out how water interacts with proteins. This is a fundamental problem that relates to protein structure, stability, dynamics and – finally – function,” said study lead author Dongping Zhong in a statement.

In the study, published in this week’s Proceedings of the National Academy of Sciences, the team showed how the much smaller and faster water molecules surround the proteins and, by pushing and pulling them, make them fold quickly.

The researchers used ultrafast laser impulses to take snapshots of the water molecules in action. In doing so, they observed water interacting with the protein’s side chains, the portions that bind and unbind with each other to fold it.

“We believe we now have strong direct evidence that on ultrafast time scales (picoseconds, or trillionths of a second), water modulates protein fluctuations,” he continued.

To better understand what they were seeing, they used computer simulations based on the data. It became clear that proteins can only fold in a certain way and that it was the way the water molecules were hitting the chains that pushed them into a certain shape.

“Here, we’ve shown that the final shape of a protein depends on two things: water and the amino acids themselves,” Zhong added. “We can now say that, on ultrafast time scales, the protein surface fluctuations are controlled by water fluctuations. Water molecules work together like a big network to drive the movement of proteins.”

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