Life secret exposed: Scientists unlock mystery of molecular machine

February 19, 2009

A major mystery about the origins of life has been resolved. According to a study published in the journal Nature, two Université de Montréal scientists have proposed a new theory for how a universal molecular machine, the ribosome, managed to self-assemble as a critical step in the genesis of all life on Earth.

"While the ribosome is a complex structure it features a clear hierarchy that emerged based on basic chemical principles," says Sergey Steinberg, a Université de Montréal biochemistry professor who made his discovery with student Konstantin Bokov. "In the absence of such explanations, some people could imagine unseen forces at work when such complex structures emerge in nature."

What is a ribosome?

The ribosome is an enormous molecule responsible for translating the messages carried in the genetic code of all organisms into the workhorse molecules of the cell - proteins - that carry out all functions, including replicating the genome itself. As the world celebrates the bicentennial anniversary of the Father of Evolution, Charles Darwin, Prof. Steinberg's theory brings the scientific community even deeper into the study of the origins of life.

By examining the molecular self-organizing processes that preceded the living cell, the point where time begins for biologists, Prof. Steinberg goes further than Darwin and the many evolutionary biologists who followed could have imagined

By the standards of biological molecules, ribosomes are immense. Though visible only through lenses of the most powerful microscopes, comparing most other biological molecules to this behemoth is like comparing a tricycle to a jumbo jet. Having spent years gazing at the detailed structure of the ribosome, Prof. Steinberg pondered how such an immense and complex structure could have assembled itself from smaller building blocks that existed on the early Earth.

From the simple to the complex

The key breakthrough came when he realized that the ribosome is organized by a set of simple structural rules and that it had to be assembled from basic building blocks in a very specific order; otherwise it would have fallen apart. He then showed with mathematical rigor that the construction of the ribosome likely followed an ordered series of steps to form the structure found in the first living cell. To this day, that structure exists almost unchanged in our own cells.

Chemists have been able to observe many examples of self-organizing behavior with simple molecules, yet explaining the complex self-assembly of biomolecules had not been so obvious.

"Thanks to the research of Sergey Steinberg and Konstantin Bokov, scientists now have a glimpse of one key event that emerged spontaneously out of the primordial chemical soup of the early Earth," explains Stephen Michnick, a Université de Montréal biochemistry professor and Canada Research Chair in Integrative Genomics. "Perhaps in the near future we may look forward to more discoveries that will take us beyond the world of Darwin into an understanding of the basic chemical principles that drove the emergence of life on our planet and perhaps beyond."

Source: University of Montreal

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mvg
5 / 5 (3) Feb 19, 2009
Not much substance to this article. A new theory, of how it "likely" happened.
Alexa
1 / 5 (1) Feb 19, 2009
Ribosomes are already known to be able to assemble spontaneously from two halves and it's really working so in test tube. The article is about evolution of ribosomal RNA. Here's some background article about it.

http://www.pubmed...d=117177
el_gramador
not rated yet Feb 19, 2009
Nice article Alexa. Not a bad research paper.
Arikin
4 / 5 (1) Feb 19, 2009
quote: "organized by a set of simple structural rules and that it had to be assembled from basic building blocks in a very specific order; otherwise it would have fallen apart."

Excuse me but what function could the first basic building block of ribosomes be in a primitive cell? If that didn't have a function why would it be built upon to eventually create a fully functional ribosome? Can a partial ribosome still synthesize proteins?
El_Nose
not rated yet Feb 20, 2009
the atricle clearly states the ribosome had none - or extremely few intermediate phases from original to our own. I don't have a degree in chemistry/biology but it never addresses the possibility of a partial ribosome.
smiffy
5 / 5 (1) Feb 20, 2009
The fact that all the active sites in the ribosome are made of RNA fits in well with the RNA-World hypothesis. I suppose that it's possible that the 70 plus proteins that make up the rest of the ribosome might just be there as improvements in efficiency. So it's possible (again guessing) that a very simple ribosome composed of just the 2 or 3 RNA strands might be sufficient to synthesize proteins. They must be a long way off demonstrating anything close to that, however.
Damon_Hastings
not rated yet Feb 23, 2009
quote: "organized by a set of simple structural rules and that it had to be assembled from basic building blocks in a very specific order; otherwise it would have fallen apart."

Excuse me but what function could the first basic building block of ribosomes be in a primitive cell? If that didn't have a function why would it be built upon to eventually create a fully functional ribosome? Can a partial ribosome still synthesize proteins?

I may not have fully understood the article, but I don't think it was saying that these "basic building blocks" were initially assembled by or within a primitive cell. I think it was saying that a ribosome could form spontaneously out of a chemical soup, with no cell required. I believe he's saying that ribosomes predate the first cell.
smiffy
not rated yet Feb 24, 2009
My reading was that because the ribosome had to be constructed in a very specific order then it's unlikely for modern ribosomes to assemble spontaneously even if the proteins were there in the chemical soup in the first place.

Sticking my neck out a bit, what the researchers may be suggesting is that the order in which the ribosome is constructed reflects that of the order in which it evolved. In principle I suppose by doctoring the DNA of a prokaryotic cell, deleting a ribosomal protein gene one at a time it might be possible to 'backwards' evolve the cell in an attempt to see just how simple the ribosome could be made and still function. I imagine that this a lot more easily said than done!

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