Courtesy of Daniela Stock
A.K. Lee et al., “The structure of the peripheral stalk of Thermus thermophilus H+-ATPase/synthase,” Nat Struct Mol Biol, 17:373–78, 2010.
Just like the turbines in a hydroelectric power plant, the revolving ‘turbine’ of the energy-generating ATPase requires a stationary component to counteract the rotation of proteins in the core. Daniela Stock at the Victor Chang Cardiac Research Institute in Sydney and colleagues used X-ray crystallography to find out what this part of the ATPase, known as the peripheral stalk, looks like. The atomic-scale resolution of the molecule revealed the secret behind the protein’s ability to remain stationary.
Electron microscopy maps can only reveal the overall shape of the outer complex, and although other subunits could be slotted into the 3D picture, this crucial component remained a puzzle. Stock’s lab managed to create a fragment of the stalk that would crystallize, and mutated key leucine residues to aid solving the structure.
The stalk’s protein sequence predicted that the structure should contain a left-handed ‘coiled-coil’—in which two alpha helices twist around each other—but key amino acids were missing. When they resolved the crystal structure they saw the first known example of a right-handed coiled-coil.
Because many rotating central proteins of the ATPases coil left, Stock hypothesizes that the right-handed coil is important because it opposes the torque generated by the rotation. “This is the last piece in the jigsaw puzzle in terms of understanding” ATPases, says F1000 faculty member Neil Marsh.
F1000 evaluators: S. Wilkens (SUNY Upstate Medical Univ.) • M. Galperin (NIH) • T. Meier (Max Planck Inst. Biophysics) • E. Marsh (Univ. of Michigan)
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