Original Repository: Library of Congress. Maxine Singer Papers
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Medical Subject Headings (MeSH):
Nucleic Acids, the Genetic Code, and Transposable Genetic Elements: A Life in Research
Thank you for your nice letter. I guess that you must now be back from Greece again and I hope that you have enjoyed your
stay there not only scientifically but also from a more touristy point of view. How about your seven year old? How did she
like Greece - the sun and the mountains and the blue sea of the clever Ulysses?
I don't know about the weather in Greece but we have had a most extraordinary summer in Sweden. Consequently I have been
extremely lazy and I have spent over a month away from the lab sailing in the Swedish archipelago which by the way has a certain
likeness to the Greece world of islands.
Your scientific results seem very pertinent and interesting to me. If I understand you correctly you propose that the RNase
II forms a complex with its polymer substrate and that this enzyme-substrate complex remains intact until the polymer is chewed
up. It would in other words not be possible to chase out a labeled polymer from the complex by adding excess cold polymer
once the enzyme-substrate complex had been formed. This would mean either that the polymer substrate is heterogenous in length
and that the enzyme has a strong preference for a certain-(shorter)-chain length or else that the substrate is so altered
in the enzyme-substrate complex that the affinity of the enzyme for the bound substrate is very much increased. If the enzyme
has no other activity towards the substrate but that of an exonuclease proceeding from the 3'-end this again would mean
that shortening the chains increases the affinity.
Your methods for preparation of nuclease free ribosomes and for the isolation of the poly U-ribosome complex look very nice
and useful. The increasing protection of poly U as the ribosome and tRNA move down towards the 3'-end is really an exciting
finding. I am sure that it will eventually become a very important analytical tool once you have tied up the loose ends that
Regarding our own activities I have written up the stuff on the enzyme-substrate complexes with valyl-AMP and tRNAval. It
has been accepted by the J. B. C. and will appear at the end of this year (I hope). I am presently writing up the purification
procedures for the enzymes which is dull work. Our main project right now is to purify that fraction of tRNAval that can
form a complex with the valyl RNA synthetase in order to study the mechanism of complex formation. This business of forming
a stable complex with its polynucleotide substrate is clearly something rather special for the valine enzyme from yeast.
Furthermore only a fraction of the tRNA chains seem to be able to form this stable complex. The important question is of
course if this phenomenon is relevant to the normal enzyme-substrate recognition process in the formation of amino acyl RNA
or whether it is some kind of biological "artifact" if you like.