Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

’Binary’ enzyme created by TSRI scientists demonstrates Darwinian evolution at its simplest

19.12.2002


Two scientists at The Scripps Research Institute (TSRI), Research Associate John S. Reader, D.Phil, and Professor Gerald F. Joyce, M.D., Ph.D., both of the institute’s Department of Molecular Biology, have succeeded in creating an enzyme based on a "binary" genetic code--one containing only two different subunits.



This research, described in the latest issue of the journal Nature, demonstrates that Darwinian evolution can occur in a genetic system with only two bases, and it also supports a theory in the field that an early form of life on earth may have been restricted to two bases.

"Nobody will ever top this because binary systems are the most reduced form of information processing," says Joyce. "Two different subunits are the absolute minimum number you need [for Darwinian evolution]."


Where protein enzymes are polymer strings made up of 20 building blocks (the amino acids), and RNA or DNA enzymes are made up of four different building blocks (the nucleotides), the world’s first binary enzyme has but two different building blocks, based on the nucleotides A and U.

This enzyme is functionally equivalent to a "polymerase" molecule. Polymerases are ubiquitous in nature as the enzymes tasked with taking a "template" string of DNA or RNA bits and making copies of it.

Reader and Joyce’s binary enzyme is able to join pieces of RNA that are composed of the same two nucleotide symbols. In the test tube, the binary string folds into an active three-dimensional structure and uses a portion of this string as a template. On the template, it "ligates," or joins subunits together, copying the template.

Experimental Approaches to the Origins of Life

If the origins of life are a philosopher’s dream, then they are also a historian’s nightmare. There are no known "sources," no fossils, that show us what the very earliest life on earth looked like. The earliest fossils we have found are stromatolites--large clumps of single-celled bacteria that grew in abundance in the ancient world three and a half billion years ago in what is now western Australia.

But as simple as the bacteria that formed stromatolites are, they were almost certainly not the very first life forms. Since these bacteria were "evolved" enough to have formed metabolic processes, scientists generally assume that they were preceded by some simpler, precursor life form. But between biological nothingness and bacteria, what was there?

Far from being the subject of armchair philosophy or wild speculation, investigating the origins of life is an active area of research and of interest to many scientists who, like Reader and Joyce, approach the questions experimentally.

Since the fossil record may not show us how life began, what scientists can do is to determine, in a general way, how life-like attributes can emerge within complex chemical systems. The goal is not necessarily to answer how life did emerge in our early, chemical world, but to discover how life does emerge in any chemical world--to ask not just what happens in the past, but what happens in general.

The most important questions are: What is feasible? What chemical systems have the capacity to display signs of life? What is the blueprint for making life in the chemical sense?

One of the great advances in the last few decades has been the notion that at one time life was ruled by RNA-based life--an "RNA world" in which RNA enzymes were the chief catalytic molecules and RNA nucleotides were the building blocks that stored genetic information.

"It’s pretty clear that there was a time when life was based on RNA," says Joyce, "not just because it’s feasible that RNA can be a gene and an enzyme and can evolve, but because we really think it happened historically."

However, RNA is probably not the initial molecule of life, because one of the four RNA bases--"C"--is chemically unstable. It readily degrades into U, and may not have been abundant enough on early Earth for a four-base genetic system to have been feasible.

Odd Base Out

To address this, Nobel Laureate Francis Crick suggested almost 40 years ago that life may have started with two bases instead of four. Now Reader and Joyce have demonstrated that a two-base system is chemically feasible.

Several years ago, Joyce showed that RNA enzymes could be made using only three bases (A, U, and G, but lacking C). The "C minus" enzyme was still able to catalyze reactions, and this work paved the way for creating a two-base enzyme.

In the current study, Reader and Joyce first created a three-base enzyme (A, U, G) and then performed chemical manipulations to convert all the A to D (diaminopurine, a modified form of A) and biochemical manipulations to remove all the G. They were left with an enzyme based on a two-letter code (D and U).

Reader and Joyce insist that their study does not prove life started this way. It does, however, demonstrate that it is possible to have a genetic system of molecules capable of undergoing Darwinian evolution with only two distinct subunits.


The article, "A ribozyme composed of only two different nucleotides," was authored by John S. Reader and Gerald F. Joyce and appears in the December 19, 2002 issue of the journal Nature.

This work was supported by a grant from the National Aeronautics and Space Administration (NASA), the Skaggs Institute for Chemical Biology at The Scripps Research Institute, and through a postdoctoral fellowship from the NASA Specialized Center for Research and Training (NSCORT) in Exobiology.

Keith McKeown | EurekAlert!
Further information:
http://www.scripps.edu/

More articles from Life Sciences:

nachricht NUI Galway highlights reproductive flexibility in hydractinia, a Galway bay jellyfish
24.02.2020 | National University of Ireland Galway

nachricht Shaping the rings of molecules
24.02.2020 | University of Montreal

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A step towards controlling spin-dependent petahertz electronics by material defects

The operational speed of semiconductors in various electronic and optoelectronic devices is limited to several gigahertz (a billion oscillations per second). This constrains the upper limit of the operational speed of computing. Now researchers from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, and the Indian Institute of Technology in Bombay have explained how these processes can be sped up through the use of light waves and defected solid materials.

Light waves perform several hundred trillion oscillations per second. Hence, it is natural to envision employing light oscillations to drive the electronic...

Im Focus: Freiburg researcher investigate the origins of surface texture

Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.

Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...

Im Focus: Skyrmions like it hot: Spin structures are controllable even at high temperatures

Investigation of the temperature dependence of the skyrmion Hall effect reveals further insights into possible new data storage devices

The joint research project of Johannes Gutenberg University Mainz (JGU) and the Massachusetts Institute of Technology (MIT) that had previously demonstrated...

Im Focus: Making the internet more energy efficient through systemic optimization

Researchers at Chalmers University of Technology, Sweden, recently completed a 5-year research project looking at how to make fibre optic communications systems more energy efficient. Among their proposals are smart, error-correcting data chip circuits, which they refined to be 10 times less energy consumptive. The project has yielded several scientific articles, in publications including Nature Communications.

Streaming films and music, scrolling through social media, and using cloud-based storage services are everyday activities now.

Im Focus: New synthesis methods enhance 3D chemical space for drug discovery

After helping develop a new approach for organic synthesis -- carbon-hydrogen functionalization -- scientists at Emory University are now showing how this approach may apply to drug discovery. Nature Catalysis published their most recent work -- a streamlined process for making a three-dimensional scaffold of keen interest to the pharmaceutical industry.

"Our tools open up whole new chemical space for potential drug targets," says Huw Davies, Emory professor of organic chemistry and senior author of the paper.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

70th Lindau Nobel Laureate Meeting: Around 70 Laureates set to meet with young scientists from approx. 100 countries

12.02.2020 | Event News

11th Advanced Battery Power Conference, March 24-25, 2020 in Münster/Germany

16.01.2020 | Event News

Laser Colloquium Hydrogen LKH2: fast and reliable fuel cell manufacturing

15.01.2020 | Event News

 
Latest News

NUI Galway highlights reproductive flexibility in hydractinia, a Galway bay jellyfish

24.02.2020 | Life Sciences

KIST researchers develop high-capacity EV battery materials that double driving range

24.02.2020 | Materials Sciences

How earthquakes deform gravity

24.02.2020 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>