Scientists using sophisticated imaging techniques have observed a molecular protein folding process that may help medical researchers understand and treat diseases such as Alzheimer’s, Lou Gehrig’s and cancer.
The study, reported this month in the journal Cell, verifies a process that scientists knew existed but with a mechanism they had never been able to observe, according to Dr. Hays Rye, Texas A&M AgriLife Research biochemist.
“This is a step in the direction of understanding how to modulate systems to prevent diseases like Alzheimer’s. We needed to understand the cell’s folding machines and how they interact with each other in a complicated network,” said Rye, who also is associate professor of biochemistry and biophysics at Texas A&M.
“But that linear sequence of amino acids is not functional,” he explained. “It’s like an origami structure that has to fold up into a three-dimensional shape to do what it has to do.”
Rye said researchers have been trying to understand this process for more than 50 years, but in a living cell the process is complicated by the presence of many proteins in a concentrated environment.
“The constraints on getting that protein to fold up into a good ‘origami’ structure are a lot more demanding,” he said. “So, there are special protein machines, known as molecular chaperones, in the cell that help proteins fold.”
But how the molecular chaperones help protein fold when it isn’t folding well by itself has been the nagging question for researchers.
“Molecular chaperones are like little machines, because they have levers and gears and power sources. They go through turning over cycles and just sort of buzz along inside a cell, driving a protein folding reaction every few seconds,” Rye said.
The many chemical reactions that are essential to life rely on the exact three-dimensional shape of folded proteins, he said. In the cell, enzymes, for example, are specialized proteins that help speed biological processes along by binding molecules and bringing them together in just the right way.
“They are bound together like a three-dimensional jigsaw puzzle,” Rye explained. “And the proteins — those little beads on the string that are designed to fold up like origami — are folded to position all these beads in three-dimensional space to perfectly wrap around those molecules and do those chemical reactions.
“If that doesn’t happen — if the protein doesn’t get folded up right – the chemical reaction can’t be done. And if it’s essential, the cell dies because it can’t convert food into power needed to build the other structures in the cell that are needed. Chemical reactions are the structural underpinning of how cells are put together, and all of that depends on the proteins being folded in the right way.”
When a protein doesn’t fold or folds incorrectly it turns into an “aggregate,” which Rye described as “white goo that looks kind of like a mayonnaise, like crud in the test tube.
“You’re dead; the cell dies,” he said.
Over the past 20 years, he said, researchers have linked that aggregation process “pretty convincingly” to the development of diseases — Alzheimer’s disease, Lou Gehrig’s disease, Huntington’s disease, to name a few. There’s evidence that diabetes and cancer also are linked to protein folding disorders.