Mahlon Hoagland on Jim Watson Brings News of Francis Crick’s Adaptor Hypothesis, 1956
  Mahlon Hoagland     Biography    
Recorded: 08 Jun 2006

At this point Jim Watson visited the laboratory. And he said, did you know that Francis Crick had already predicted the existence of a molecule like this? And I said no,. and I said what business is it of yours to tell me something like that when I am working on this problem.

Jim was absolutely delighted with our discovery and very quickly Francis learned about it and came to our laboratory to visit and see our results.

That was—early ’56, 1956. Francis was enormously intrigued at the because he had predicted the existence, the necessity of such a molecule to exist. Namely amino acid had no chemical similarity or complementarity to RNA which presumably was the template for protein synthesis namely RNA was a structure that was on the ribosome and presumably determined the sequence of amino acids and protein. But there was no chemical relationship between amino acids and RNA so how would an RNA template recognize which amino acids to put where in the order. Francis suggested that if you adapted the amino acid so that it could recognize the template by attaching it to a small piece of RNA then that small piece of RNA could go to the template sit down in the right place and determine the location of the amino acid attached to it.

So Jim comes to the laboratory and tells me that Francis had already suggested this. We had already at this time realized that this must be what this is doing, but we had no proof at all. This led to my going to Francis’s laboratory for a year to spend some time with him. By that time the code was being worked out namely how many nucleotides would be needed to identify an amino acid and put it the right place in a protein chain and that was three, a triplet code which we now know is the definitive code. So he suggested that the amino acid might first be attached to a small RNA perhaps as small as three nucleotides and that this would be what would determine—it turns out that transfer RNA the molecule that was actually attached to it is a much more complex molecule of some seventy nucleotides.

Mahlon Hoagland, a molecular biologist who was one of the discoverer of the transfer ribonucleic acid - tRNA. He received a medical degree from Harvard Medical School in 1948. He served as a doctor during the Second World War. When the War ended he returned to Harvard and became researcher in the Huntington Laboratories at the Massachusetts General Hospital in Boston. He worked in the bacteriology and immunology department of Harvard Medical School from 1952 till 1967.

Working together with Paul Zamecnik and Elizabeth Keller he discovered the initial steps of protein synthesis. Two years later in 1958 Hoagland and Zemecnik discovered tRNA. His main input to the laboratory was in his work with amino acid activating enzymes. He noticed that certain enzymes were required to activate amino acids so they could combine with tRNA molecules and eventually be incorporated into new protein molecules. These enzymes were named aminoacyl tRNA synthetases.

In 1957 Hoagland moved to Cambridge where he worked for a year with Crick at Cambridge University. Working together they tried to explain the genetic code. He was Associate Professor of Microbiology at Harvard Medical School and in 1967 was appointed professor in the biochemistry department at the Dartmouth Medical School. After 3 years he left Dartmouth and became Director and President of the Worcester Foundation for Experimental Biology in Massachusetts. He retired in 1985.

Mahlon Hoagland was awarded the Franklin Medal for life science. He was a member of the American Academy of Arts and Sciences and the US National Academy of Sciences. He died on September 19, 2009.

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