New study details one of biology's largest proteins

"We chopped up the protein into five parts and studied it using different methods," said researcher Ilja Voets.
By Brooks Hays   |   Aug. 9, 2017 at 5:53 PM
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Aug. 9 (UPI) -- Scientists have discovered one of the largest proteins in nature. The protein serves as an anchor for the unique bacterium living in the frigid waters of Antarctica.

The protein MpAFP, an "adhesion" measuring 600 nanometers in length, helps the Marinomonas promoryiensis bacterium attach itself to ice.

Scientists hope their analysis of the protein structure -- detailed this week in the journal Science Advances -- can help researchers better understand how harmful bacteria adhere to human cells, and ultimately prevent them from doing so.

"This is a first for such an adhesin," Shuaiqi "Phil" Guo, a postdoctoral researcher at the Eindhoven University of Technology in the Netherlands, said in a news release. "Moreover, it is one of the biggest proteins ever to be detailed. At a length of 600 nanometers, it is a giant compared with most proteins of between 2 and 15 nanometers in size."

The protein was too large to image it using traditional 3D imaging techniques. Most proteins are crystallized and imaged whole, but not MpAFP.

"We chopped up the protein into five parts and studied it using different methods," said Ilja Voets, a researcher at TU/e. "Apart from x-ray diffraction, we also used x-ray scattering, a specialist field of ours in Eindhoven, and nuclear magnetic resonance."

Scientists then pieced the individually imaged pieces back together to form a complete 3D model.

The researchers' analysis showed the different sections of the protein perform specialized functions. In addition to adhering to icy surfaces, the anchor-like protein also helps the bacterium attach to photosynthesizing organisms, providing the bacterium with energy from the sun. The bacterium tends to stay close to the ocean surface where there is more light and more light-harvesting organisms.

Researchers hope that by detailing how Marinomonas promoryiensis uses MpAFP to grip onto ice and other organisms, they can find a way to thwart the protein anchor and prevent harmful bacteria from adhering to human cells.

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