A team of Massachusetts General Hospital (MGH) investigators working to create "protocells" primitive synthetic cells consisting of a nucleic acid strand encased within a membrane-bound compartment have accomplished an important step towards their goal. In the November 28 issue of Science, the investigators describe a solution to what could have been a critical problem the potential incompatibility between a chemical requirement of RNA copying and the stability of the protocell membrane.
"For the first time, we've been able to do nonenzymatic RNA copying inside fatty acid vesicles," says Jack Szostak, PhD, of the MGH Department of Molecular Biology and the Center for Computational and Integrative Biology. "We've found a solution to a longstanding problem in the origin of cellular life: RNA copying chemistry requires the presence of the magnesium ion Mg2+, but high Mg2+ levels can break down the simple, fatty acid membranes that probably surrounded the first living cells."
Szostak's team has been working for more than a decade to understand how the first cells developed from a "primordial soup" of chemicals into living organisms capable of copying their genetic material and reproducing. Part of that work is developing a model protocell made from components probably present in the primitive Earth environment. They have made significant progress towards developing cell membranes from the kind of fatty acids that would have been abundant and naturally form themselves into bubble-like vesicles when concentrated in water. But the genetic component an RNA or DNA molecule capable of replication has been missing.
Since the primitive environment in which such cells could have developed would not have had the kind of complex enzymes that modern cells use in replicating nucleic acids, Szostak and lead author Katarzyna Adamala, PhD, then a graduate student in Szostak's lab, investigated whether simple chemical processes could
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Massachusetts General Hospital