Steven Ludtke, a Baylor assistant professor of biochemistry and molecular biology, found such dynamic behavior in a mutant form of a protein called GroEL, which helps misfolded protein achieved their purpose in cells.

Ludtke and colleagues at the University of Texas Southwestern Medical Center used electron cryomicroscopy to take detailed two-dimensional images of molecules in a native-like environment. Then they assemble tens of thousands of such images into three-dimensional models that demonstrate the dynamics of the proteins.

When the team followed that procedure with the GroEL mutant with its sister-protein, GroES, they found two of the structures were as they expected but the third was "a strange-looking structure blown up like a balloon."

"This sort of expansion has never been observed before," he said. "The expansion was directly related to the function of the assembly. From a more global perspective, this is strong evidence that we need to study how any macromolecule behaves in a solution environment."

The research is explained in the current issue of the journal Structure.