Biomolecular structure

Bacteria’s amyloids display surprising structure

 amyloid-like clumps made by bacteria
PROTEIN POWER Proteins from Staphylococcus aureus bacteria make amyloid-like clumps (the streamerlike structures in this illustration) that are toxic to human cells.

Clusters of a toxic bacterial protein have a surprising structure, differing from similar clumps associated with Alzheimer’s and Parkinson’s in humans, scientists report in the Feb. 24 Science.

These clusters, called amyloids, are defined in part by their structure: straight regions of protein chains called beta strands, folded accordion-style into flat beta sheets, which then stack up to form a fiber. That definition might now need to be broadened.

“All the amyloids that have been structurally looked at so far have certain characteristics,” says Matthew Chapman, a biologist at the University of Michigan in Ann Arbor who wasn’t part of the work. “This is the odd amyloid out right now.”

In the human brain, misfolded proteins can form amyloids that trigger neurodegenerative diseases. But amyloids aren’t always a sign of something gone wrong — some bacteria make amyloids to help defend their turf.

In Staphylococcus aureus, for example, the PSMα3 protein assembles into amyloids that help the bacteria kill other cells. Previous…

How to view tiny parts of DNA? Make them ‘blink’

chromosome flash
chromosome flash

A single chromosome, here, has blinked on brightly, after being excited by light. That light being emitted by the genetic tissue makes internal cellular structures visible without the need for fluorescent dyes.

BOSTON, Mass. — A new technique can home in on parts of a cell that are smaller than 10 nanometers (billionths of a meter) in size without damaging the cell. On February 17, Vadim Backman described how he and his group makes cells do this. They take advantage of DNA’s natural ability to “blink” on when hit with the right color of light.

Backman and Hao Zhang work at Northwestern University in Evanston, Ill. Together, the biomedical engineers found a way to make some materials in a cell briefly shine more brightly than if they had been labeled with one of the most powerful fluorescent chemicals. Their trick: They tickle cells with a particular wavelength — or color — of light.

Backman presented the details, here, at the annual meeting of the American Association for the Advancement of Science. This new approach, he argues, can offer views…