X-ray Footprinting technique reveals the mystery of metal-breathing protein


X-ray Footprinting

Scientists discovered an information of unusual coupling between bacterial protein and mineral, allows the bacterium to breathe when oxygen is unavailable.

The research leads to new revolutions in linking proteins to other materials for bio-based electronic devices. It could also help researchers to understanding and control of the chemical reactions sparked by these protein-material interactions.

“Moving electrons to metals can cause different minerals to grow or dissolve. Studying how a protein does this can help us understand how an organism remodel their environment and make biominerals for teeth or protection,” said, Caroline Ajo-Franklin, a staff scientist at Berkeley Lab’s Molecular Foundry.

Researchers relied on an X-ray based technique, known as “footprinting,” to point the chemical connections between the bacterial protein and nanoparticles composed of iron and oxygen. However, they identified a small and weak binding structure.

The structure of this exotic protein already mapped in isolation with atomic-scale. But, scientists didn’t know how it bound to the metal-containing mineral conventional techniques can’t see this binding process.

Researchers said, Footprinting explains the interaction of proteins. It provides structural and dynamic information about proteins in close to their native environment. The protein selected for the study is from a metal-reducing bacteria, Shewanella oneidensis, which eats sugar and breathes minerals, when oxygen is unavailable.

hydroxyl radicals

Researchers found a way to prepare the protein and nanoparticles in a liquid solution for X-ray studies. In FootPriniting, X-rays produce hydroxyl radicals, which are highly reactive molecules. These radicals pass through the liquid solution surrounding the protein. The radicals modify the protein and allows scientists to pinpoint slight chemical variations where the protein is in touch with the solution.

The regions of the protein interacts with other proteins or materials are protected from the radicals. The locations where the protein is not altered indicate where the binding occurs.

The new study said, these chemical snapshots produced by the X-ray footprinting technique at different points in time and subsequently analyzed using a technique, mass spectrometry.

Ajo-Franklin said, most proteins interface with materials bind tightly, and change shape as they form this connection. This particular protein doesn’t changes shape, and only interacts with the mineral in a small area, requiring about five times less binding energy than typical proteins that form biominerals.

However, the task of this protein is to transfer electrons to the mineral. The research team now working to study how this and similar proteins interact with a range of minerals.

More information:[JACS]