Please reply to
Genetica Building

April 12, 1955

Dr. Boris Rotman
Instituto de Cuinica Mstologica
Santiago, Chile

Dear Sorlse

The last couple of weeks have been the culmination of feverbsh activity;
now that the sympesium we had here on Genetics in Medical Research if over
we can look forward te sone repose and to return to our usual cain pace.

I saw Hoecker at the Gatlinburg meeting, and was glad to have you revards,
which T warmly return,

AS you know, we and <alekar have been engaged in a rather distent collabore~
tion on the enzymology and genetics of the various galactose mutants of E. coli.
With the help of the lambda-linked transduction, wo have what {ig probably the
most detailed genetic information on these genes that can be obtainal anywis re.

So far, Esther (and previously Larry Morse) has sccumlated hundreds of mutants
which are still being analysed. You are probably fantliar with the already
yublished results that many of the mutants fall into two groups, which we will

aow call X and T, The K maitants (Gala; Gal.) show a simple defect in valabtokinase;
the T mutants (Galj; Gal, etc.) are deficient in uridine-di phosphosphohexose
transferase, Further more the T and the X group constitute each a simple cistror.
when tested in heterogenotes, So far so good. “fore recently Esther mak gharacteri cod
another mutant Galo aa giving position effects yith heth the 4 and the T cistrone;
furthermore, this fs the first isolate which is deficient in the third of the
galactose enzymes, the uridine disphosphohexose epimerase; it is also weak or
deLicient in the other two enzymes! Kalckar is now pursuing the Interesting ques
tien whether Galo when gram in the absence of Zalactoss is entirely devoid of
this suger in ite cell wall strueture.

dow, Kalckar visited Madison during the syuposiua and we nad a chance toe review
the strategy for a more coordinated attack on this attractive problan, which we
feel we wust do. Herman has of course many other commitments end, since Kiyostd
Kurabashi left his group at the NIH, ne has been working eveninzs as test he gan
ou these questions. You may not kmow that he has accepted a rather exciting posi-
tion in the Biology Departuent (MeCollur Pratt Institute) at Johns lopkins, effer
tive tals summer, and this should 4mpreve the opportunities for collaboration,

Tt turns out that “alckar gay be able to sponser a suitable position in his
sroup at Johns Hopkins, Of course, 1t imvediately occurred to me that you would be
the most plausible person to try to interest in this prograa, anvil Kelecerts imme-
diate response was quite encouraging. Frou what I could learn of 44, the posttion
show be an excelleht opportunity, so om several counts I hope it micht be attrae~
tive to you. In view of your plans for visitias the IE this fall, *% looked ab 42
it might be practical te verk somethings out. TI dant) nave te tell you how deli ghted
we would be to be able to renew our acientifie interaction,
If, as I hope, you might be interested in this possibility, I suggest”
you write directly to Kalckar (c/o NIH, Bethesda 14 Md.) mentioning this
letter and including a biography.

Of course the detailed planning will have to wait until your participation.
However, the Gal system is on the verge of being ready for such approaghes
as the isolation of the separate enzymes, immunological characterization of
mutant products, the effect of transduced fragments of DNA in initiating
enzyme synthesis and so forth, For this reagon I believe it represents an
unusual challangg for an approach which has some realistic prespects of
answering some of the most fundamental questions fn gene-enzyme relationships/

With all best regards,

Yours, as ever,

Joshua Laderhers