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 transfer RNA (tRNA). They used the powerful X-rays produced by the Advanced Photon Source at Argonne National Laboratory to obtain images from crystals formed by these two RNA molecules. 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 Mondragn, 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 catalyst 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," Mondragn said. "We now have a better understanding of how RNA works."
RNase P is formed by a large RNA core plus a small protein, illustrating the evolutionary shift from an RNA world toward a protein-dominated world. The protein helps recognize the
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