Molecular fossil: Crystal structure shows how RNA, one of biology's oldest catalysts, is made

November 14, 2010
Molecular fossil: Crystal structure shows how RNA, one of biology's oldest catalysts, is made
The crystal structure RNase P, composed of a large RNA subunit (blue) and a small protein component (green), shown in complex with tRNA (red). The RNA component serves as the primary biocatalyst in the reaction.

( -- In today's world of sophisticated organisms proteins are the stars. They are the indispensible catalytic workhorses, carrying out the processes essential to life. But long, long ago ribonucleic acid (RNA) reigned supreme.

Now Northwestern University researchers have produced an atomic picture that shows how two of these very old molecules interact with each other. It is a rare glimpse of the transition from an ancient, RNA-based world to our present, protein-catalyst dominated world.

The scientists are the first to show the atomic details of how ribonuclease P (RNase P) recognizes, binds and cleaves (tRNA). They used the powerful X-rays produced by the at Argonne National Laboratory to obtain images from crystals formed by these two . The result is a snapshot of one of the most complex models of a catalytic RNA and its target.

Details of the structure will be published Nov. 14 by the journal Nature.

"RNA is an ancient molecule, but it is pretty sophisticated," said Alfonso Mondragón, professor of molecular biosciences in the Weinberg College of Arts and Sciences. He led the research. "Our crystal structure shows that it has many of the properties we ascribe to modern molecules. RNA is a that has much of the versatility and complexity of modern-day proteins."

For billions of years and still to this day, the function of RNase P -- found in nearly all organisms, from bacteria to humans -- has been to cleave transfer tRNA. If the tRNA is not cleaved, it is not useful to the cell.

"We knew this important chemistry happened, that RNA acts as a catalyst, but we didn't know exactly how until now," Mondragón said. "We now have a better understanding of how RNA works."

RNase P is formed by a large RNA core plus a small , illustrating the evolutionary shift from an RNA world toward a protein-dominated world. The protein helps recognize the tRNA, but most of the recognition occurs through RNA-RNA interactions involving shape complementarity and also base pairing.

The structure shows that once RNase P recognizes tRNA, it docks and, assisted by metal ions, cuts one chemical bond. This matures the tRNA, producing a smaller RNA molecule that now can contribute to fundamental processes in the cell. The RNA-based enzyme does this over and over, cutting each tRNA in exactly the same place every time.

"The discovery nearly 30 years ago that RNA molecules can have a catalytic function raised the idea that maybe RNA was the first molecule," Mondragón said. "Our work reinforces this notion of the existence of an RNA world when life first began."

Explore further: 'Accelerated evolution' converts RNA enzyme to DNA enzyme in vitro

More information: The title of the Nature paper is "Structure of a bacterial ribonuclease P holoenzyme in complex with tRNA."

Related Stories

New compound effectively treats fungal infections

June 22, 2007

A new mechanism to attack hard-to-treat fungal infections has been revealed by scientists from the biotech company Anacor Pharmaceuticals Inc., California, and the European Molecular Biology Laboratory (EMBL) outstation in ...

A Molecular Identity Crisis - a 'Ribozyme Without RNA'

November 3, 2008

( -- Not all enzymes that are assumed to require an RNA component in order to function do actually contain RNA. This surprising discovery was made during a project supported by the Austrian Science Fund FWF that ...

Recommended for you

A new form of real gold, almost as light as air

November 25, 2015

Researchers at ETH Zurich have created a new type of foam made of real gold. It is the lightest form ever produced of the precious metal: a thousand times lighter than its conventional form and yet it is nearly impossible ...

Getting under the skin of a medieval mystery

November 23, 2015

A simple PVC eraser has helped an international team of scientists led by bioarchaeologists at the University of York to resolve the mystery surrounding the tissue-thin parchment used by medieval scribes to produce the first ...

Moonlighting molecules: Finding new uses for old enzymes

November 27, 2015

A collaboration between the University of Cambridge and MedImmune, the global biologics research and development arm of AstraZeneca, has led researchers to identify a potentially significant new application for a well-known ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.