Featured Research

from universities, journals, and other organizations

"Binary" Enzyme Created By Scripps Scientists Demonstrates Darwinian Evolution At Its Simplest

Date:
December 19, 2002
Source:
Scripps Research Institute
Summary:
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.

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.


Story Source:

The above story is based on materials provided by Scripps Research Institute. Note: Materials may be edited for content and length.


Cite This Page:

Scripps Research Institute. ""Binary" Enzyme Created By Scripps Scientists Demonstrates Darwinian Evolution At Its Simplest." ScienceDaily. ScienceDaily, 19 December 2002. <www.sciencedaily.com/releases/2002/12/021219065007.htm>.
Scripps Research Institute. (2002, December 19). "Binary" Enzyme Created By Scripps Scientists Demonstrates Darwinian Evolution At Its Simplest. ScienceDaily. Retrieved October 23, 2014 from www.sciencedaily.com/releases/2002/12/021219065007.htm
Scripps Research Institute. ""Binary" Enzyme Created By Scripps Scientists Demonstrates Darwinian Evolution At Its Simplest." ScienceDaily. www.sciencedaily.com/releases/2002/12/021219065007.htm (accessed October 23, 2014).

Share This



More Matter & Energy News

Thursday, October 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Chameleon Camouflage to Give Tanks Cloaking Capabilities

Chameleon Camouflage to Give Tanks Cloaking Capabilities

Reuters - Innovations Video Online (Oct. 22, 2014) — Inspired by the way a chameleon changes its colour to disguise itself; scientists in Poland want to replace traditional camouflage paint with thousands of electrochromic plates that will continuously change colour to blend with its surroundings. The first PL-01 concept tank prototype will be tested within a few years, with scientists predicting that a similar technology could even be woven into the fabric of a soldiers' clothing making them virtually invisible to the naked eye. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Jet Sales Lift Boeing Profit 18 Pct.

Jet Sales Lift Boeing Profit 18 Pct.

Reuters - Business Video Online (Oct. 22, 2014) — Strong jet demand has pushed Boeing to raise its profit forecast for the third time, but analysts were disappointed by its small cash flow. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com
Internet of Things Aims to Smarten Your Life

Internet of Things Aims to Smarten Your Life

AP (Oct. 22, 2014) — As more and more Bluetooth-enabled devices are reaching consumers, developers are busy connecting them together as part of the Internet of Things. (Oct. 22) Video provided by AP
Powered by NewsLook.com
What Is Magic Leap, And Why Is It Worth $500M?

What Is Magic Leap, And Why Is It Worth $500M?

Newsy (Oct. 22, 2014) — Magic Leap isn't publicizing much more than a description of its product, but it’s been enough for Google and others to invest more than $500M. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:

Strange & Offbeat Stories

 

Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins