GOTEBO RGS U NlVE RSlTET
Medicinsk-Kemiska Institutionen
   Medicinaregatan 9
    Goteborg SV

--

22 August, 1966.

Dr. Maxine Singer
National Institutes of Health
BETHESDA, M.D. 20014, U.S.A.

Dear Maxine,

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 wheather in Greece but we have had a most

extraordinary summer in Sweden.
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 is land s .

Consequently I have been extremely

Your scientific results seem very pertinent and interesting to me.

If I

understand you correctly you propose that the RNase I1 forms a complex
with its polymer substrate and that this enzyme-substrate complex remains
intact until the polymer is chewed up.
possible to chase out a labelled polymer from the complex by adding excess
cold polymer once the enzyme-substrate complex had been formed.
wouldmean 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.

It would in other words not be

This

Your methods for preparation of nuclease free ribosomes and for the
                                                The

isolation of the poly U-ribosome complex look very nice and useful.
increasing protection of poly U as the ribosome and tRNA move down towards
the 3' -end is really an exciting finding.
become a very important analytical tool once you have tied up the loose ends
that you mentioned.

I am sure that it will eventually

2.

Regarding our own activities I have written up the stuff on the enzyme-

substrate complexes with valyl-AMP and tRNA
the J. B. C. and will appear at the end of this year (I hope).
writing up the purification procedures for the enzymes which is dull work.
Our main project right now is to purify that fraction of tRNA
form a complex with the valyl RNA synthetase in order to study the
mechanism of complex formation.
with its polynucleotide substrate is clearly something rather special for

Val

the valine enzyme from yeast.  Furthermore only a fraction of the tRNA
chains seem to be able to form this stable complex.
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.

It has been accepted by
     I am presently

Val'

that can

Val

This business of forming a stable complex

The important

With best regards to you and your family

Since rely

Ulf Lag rkvist