College of LAS « Illinois

Physics

Atom-by-Atom Action Shots

First-ever snapshot of ribosome in action has medical ramifications.

Gumbart-Schulten

Capturing action on camera is difficult. Just ask any sports photographer who has tried to capture a frozen moment in football. But trying to take action shots on the microscopic level, with atom-by-atom detail, has been beyond the current technology—until now. LAS researchers, working with scientists in Germany, have found a way to take the first detailed picture of a ribosome in action.

“We were able to get the first snapshot ever that sees a newly born protein moving out of a ribosome and into a SecY channel and then into the cell’s membrane,” says Klaus Schulten, University of Illinois physics and biophysics professor. What’s more, this picture is a detailed action shot, depicting the roughly 3 million atoms that make up the ribosome and other players on the microscopic field.

Ribosomes are found in every living cell, and they carry out a central function—to read genetic information for the synthesis of protein. They also play an important role in the development of antibiotics, so seeing them in action has important medical benefits.

The U of I work builds upon research by the 2010 Nobel-winning scientists who determined the structure of the ribosome in crystallized form. Schulten says that in crystallized form, “the ribosomes all stand at attention and don’t do very much because they are closely packed together.”

He compares it to taking a photograph of football players lined up on the sidelines singing the national anthem. “You can see the players, but if you want to teach someone how the players function on the field, a photograph of them on the sidelines doesn’t tell you very much. You need to take a picture of the players in action.”

So Schulten and physics graduate student James Gumbart set out to do just that. They worked with Roland Beckmann at the University of Munich, who had captured the action of a ribosome with electron microscopy. The problem was that the images were fuzzy.

“Electron microscopy doesn’t see the detail,” Schulten points out. But the U of I team successfully brought these fuzzy images into focus by filling in the details with a “computational microscope”—a computer program developed by Schulten and others at the U of I.

This image shed new light on how a protein threads itself into a cell membrane. About half of the drug targets for antibiotics are proteins that move from the ribosome into the cell membrane of bacteria, making these proteins extremely important in the ongoing war against bacterial infections.

“So understanding the ribosome better and how an antibiotic interferes with it is very relevant,” he says. “It may be one of the most important things we can do right now in medicine.”

Fall 2011