Bottles of water. (Credit: Jo McCulty / Ohio State University)
Why is water so important for life? Scientists at Ohio State University have come one step closer to finding out. The importance of water to life, they say, has to do with its roles in the folding of proteins.
Proteins are large and complex molecules that fold into specific shapes and make biological reactions possible — and they can’t fold themselves without the aid of water. Or more specifically, researchers say, smaller water molecules surround the proteins and push and pull them as needed to make them fold in just fractions of a second.
To make the determination, investigators at the university used super-fast, pulsing lasers to gather snapshots of water molecules as they danced around a DNA polymerase. The enzyme is essential to how DNA strands replicate. But scientists still needed a good way to track the protein’s shifts, so they injected tryptophan as a probe to see how water molecules moved around it.
The researchers determined that the water molecules directly touched the protein’s “side chains,” or the portions of the protein molecule that bind and unbind with each other to enable folding and function. They also were able to note the timing of movement in the molecules. Beyond that, computer simulations at the Ohio Supercomputer Center let the researchers visualize what was happening.
Scientists saw that the protein folded nanoseconds later when the water moved a certain way. It was as if the water molecules were nudging the protein into shape.
Researchers note that the shapes proteins take aren’t arbitrary. That is, they can only fold a few different ways depending on the amino acids that they’re made of. Those acids, along with water molecules, are the two most important factors when it comes to determining protein shape.
Investigators conclude that protein surface fluctuations are controlled by water fluctuations on ultrafast time scales, and that water molecules work together like a big network to drive protein movement.
Top image: Bottles of water. (Credit: Jo McCulty / Ohio State University)