A reducibly simple cell?

New Way To Think About Earth's First Cells

(ScienceDaily.com, 6/6/2008)

A team of researchers at Harvard University have modeled in the laboratory a primitive cell, or protocell, that is capable of building, copying and containing DNA. Since there are no physical records of what the first primitive cells on Earth looked like, or how they grew and divided, the research team's protocell project offers a useful way to learn about how Earth's earliest cells may have interacted with their environment approximately 3.5 billion years ago.

The protocell's fatty acid membrane allows chemical compounds, including the building blocks of DNA, to enter into the cell without the assistance of the protein channels and pumps required by today's highly developed cell membranes. Also unlike modern cells, the protocell does not use enzymes for copying its DNA.

Led by Jack W. Szostak of the Harvard Medical School, the research team published its findings in the June 4, 2008, edition of the journal Nature's advance online publication.

"Szostak's group took a creative approach to this research challenge and made a significant contribution to our understanding of small molecule transport through membranes," said Luis Echegoyen, director of the NSF Division of Chemistry.

When the team started its work, the researchers were not sure that the building blocks required for copying the protocell's genetic material would be able to enter the cell.

"By showing that this can happen, and indeed happen quite efficiently, we have come a little closer to our goal of making a functional protocell that, in the right environment, is able to grow and divide on its own," said Szostak.

"We have found that membranes made from fatty acids and related molecules -- the most likely components of primitive cell membranes -- have properties very different from those of the modern cell membrane, which uses specialized pumps, channels or pores to control what gets in and out," says Jack Szostak, PhD, of the MGH Department of Molecular Biology and Center for Computational and Integrative Biology, the report's senior author. "Our report shows that very primitive cells may have absorbed nutrients from their environment, rather than having to manufacture needed materials internally, which supports one of two competing theories about fundamental properties of these cells."