Magazine article Science News

Yeast Peptide Goes Forth and Multiplies

Magazine article Science News

Yeast Peptide Goes Forth and Multiplies

Article excerpt

Even the most efficient corporation would envy the teamwork exhibited by the molecules in a cell. At some point, though, before the first cells appeared on Earth, organic molecules would have been on their own, replicating without help from others. So far, scientists studying the origin of life have come across RNA-like molecules that can perform this trick, but no one had proved that proteins could do the same - until now.

Researchers have found the first evidence that peptides, short chains of the amino acids that make up proteins, can copy themselves by aligning and joining two pieces. Since much of the effort to understand the origin of life has focused on RNA (SN: 11/26/94; 8/10/96, these results may broaden the thinking on self-replication in biological molecules, some scientists say. Whether the results will influence theories about the origin of life, however, must be determined by further studies. The ideas may also lead to new ways of synthesizing chemicals.

M. Reza Ghadiri and his colleagues at the Scripps Research Institute in La Jolla, Calif., demonstrated self-replication in a peptide. Made of 32 amino acids wound into a tight helical structure, the peptide came from a yeast protein that regulates the activity of genes in the cell. The scientists reported their results in the Aug. 8 Nature.

The researchers took two near-halves of this peptide, one segment with l5 amino acids and the other with 17, and allowed them to react in solution. They saw that the presence of completed peptides caused the segments to assemble at up to 500 times the expected rate.

The peptides catalyzed the reaction, acting as matchmakers. The segments lined up alongside the full molecule, coming close to each other in an orientation amenable to bonding. Otherwise, the segments would have been left to bump into each other at random while floating in the vast solution. …

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