Image captures ‘streamlined essence of what life entails’

In a first, St. Jude scientists captured the atomic structure of a mechanism for unwinding DNA. Double-stranded DNA must separate before it’s copied and the cell divides.

The image shows an enzyme complex bound to single-stranded DNA along with the molecules that fuel unwinding. The structure of the enzyme complex, called the MCM complex, was known. But how the process worked was a mystery.

Imagine a winch that lifts a bucket from a well. Scientists suggested that the ring-shaped MCM complex might function in a similar way and pull one DNA strand through its central pore.

“The structure could also provide the physical basis for getting DNA replication started,” said Eric Enemark, PhD, of the St. Jude Department of Structural Biology. “This single event is at the heart of cell division. Arguably, it’s the streamlined essence of what life entails.”

A report on this work appeared in Nature Communications.