Bio Students Make Genetic Breakthrough

Two graduate students in biology have brought biologists one step closer to cracking the genetic code.

In a paper to be published in June. Mario R. Capecchi says that in a typical bacteria. E. coli, one special amino acid is probably required to initiate the synthesis of all proteins. He suggests that this some amino acid may be necessary for the initiation of all protein synthesis.

Last night, University Professor John T. Eisell termed the research "a really important development, and a clue to a very general pattern of how protein synthesis gets started."

In the process of protein synthesis, information is transferred from DNA, a linear sequence of nucleotides, to messenger-DNA another type of nucleic acid. The messenger is then "read" and amino acids corresponding to the "words," or codens are joined together end-to-end in a long chain to form a protein.

It is known that one messenger sometimes codes for more than one protein. However, it was not understood how the cell "punctuated" the message to separate one protein from the next: the chain of the first protein must be terminated right before the first amino acid of the second protein. For a while it was thought that the only signal required was a special codon in the messenger that said "stop."

But last fall Capecchi and Jerry M. Adams, another pre-doctoral student at the Biology labs, found evidence that an initiator signal was also required, and that part one of this signal was the amino acid N-formylmethionine.

Verification of their hypothesis in living systems was complicated by the presence of an enzyme which removed the initiator from chains as soon as the chains were completed. They got around this difficulty by first working with in vitro viral systems.

Now Capecchi has found that the amount of this amino acid found in E. coli is consistent with their proposal. And within a few months, he believes, we may know if this scheme can be generalized to all systems, including mammals.