February 25, 1958

Dr. Herman MW. Kalckar
Rational Institutes of Health
Bethesda 14, Maryland

Dear Herman:

I was very glad to hear that you were able to straighten ont the
question of travel expense. We are looking forward to seeing you here.
As a matter of fant the tim during the meetings will be so busy that
there may be relatively little occasion for us to get together privately.
Would you consider staying over another day 20 that we might have sone
ohance for quiet discussion? There are a nuaber of things I really want
te pin you down on.

Of course we are even more pleased to hear of the renewal of your
interests in the Gal problem. I realize of course that you are pre-~
cocupied by many cther distractions and that having lost Kiyosha to
another program would not help the continuity of cur collaboration.
However if you will lock through the correspondence I think you will
eee that we have had auch too sketchy a picture of what has becr going
om and too often we could get our first clear lapreseions only from the
rather condensed version of a hasty smsnuscript. Now that the most excit-
ing initial features have in a sense passed, I think that we oan perhaps
settle down to a more confidered discussion.

One point of confusion that has never been clenred up for me is the
extent of inducabllity of the various enzyms in wild type E. colt.
Kiyosha once promised to send me the qiantitative data on this point but
never has. I am by no means very happy about the use of nutriant aedia
for the bulk of the experiments aa I am sure this would cbseure induc-~
tion effects.

As I am mure you realize the eutant step has been worked on until
now represents the siaplest asses and they of course did give the very
exciting result of corrolating two genetic cistrons with two specific
ensymes. In apite of the speculation on such pointes elsewhere, I think
this was the first real verification of that idea. But Eather and I are
both a little comeerned about too hasty a generalisation, especially
when this is based on @ selected aasple of mutants. The Gal, case will
ba @h example. It is just as pussling to us why this should’ seea to
belong to two cistrons as its ensymatic behavior is puzzling to you.
But until this 4s cleared up on both sides I think it stands as a serious
challenge to the simple hypothesis. Recently Esther sent you another
Dr. Herman M. Kalckar
Page 2 — February 25, 1958

culture labeled Galo. This seems to be genetically analogoup to Gal,
but is distinct from it by recombimtion test. If it should prove
have the samp bicchemioal behavior as Gal; it would indicate that this
is a significant clase of mutants and not an exception worthy of being
ignored. It will then, it seems to m, be extremely important to find
out what its defect 1s in the mtaboliom of galactose.

If we had not made it clear before the essential genetic informa-
tion about Gal3, (and the sam for Qalg) is this: it is a distinct
mutant, different by recombination test from every other one tested.

It is therefore unlikely to be a simple deletion euch as Benser has
described, because such a type would be expected to Le apparently the
sam, by recombination test, with a number of other mutants. Further-
more it dogs show occasional reverse mutation ani therefore is equally
unlikely to be a simple deletion. However when heterogenctes are made
beteeen Galy eni any of the mutants either from the Gal, or the Gal
cistrons, typical position effects are seen. This is, } think, contrary
to any slaple picture of the organization of the genetic material into
discrete cistrons. It might help however to know what the enapmplogical
effact is.

Ye have, as you known, at least 59 other mtants but we are not
going to bother you with thea unleas we find som peculiarity that
would warrant more detailed analysis. ‘They are belng systematically
screened for their cistron behavior and we will let you know the picture
4f any further sxeeptions appear, He ure also testing all of the mutants
for the temperature sensitivity 2t least as far as their growth fermenta-
tive ability is concerned. #¢ are also soreening all of the existing
matants, and looking for a graat many more, from the point of view of
dependence on gilectose, otviously in the hope that these aight reflect
the aissing class of atisurase mutants.

Our failure to find etimerase matante sao far may de a consequonce
of the inability of auch autants to grow even on a medium containing
galactose. Do you suppose there would be very much point in adding UDP
Gal to our complete medium? If not this, can you suggest any other
supplements which aight be used instead? If we do use UDM Gal, do you
suggest we use the commercial mterials obtainable from the Jigma Company
or can you suggest a better source?

Still another possibility, it seems to me, is that an etiasrase
maitant may not appear to be galactose negative on our usual test. Can
you think of any by-pass mechaniems that weuld take the plaee of the
etimsrase? Of course there is the remaining possibility that UDP Gel
might be quite toxic if accumulated inside the cell.

We will be very happy to have your comments on these points.
Dr. Herman M. Kalckar
Page 2 - February 25, 1958

Do you remember 831427 We still do not have the last word on this
bat there is now some reason to believe that it is a double mtant. One
of the factors may be a fairly typical Gal- linked in the other cistron.
The other factor would either prevent efficient transduction to the strain
or might be a modifler resulting in "slow" fermmtation. The whole story
da not af all finished but I thought you alght want to know this current
interpretation. In any case the publication last year was highly pre-
ature a.nd IT hope we can have more effective communication on both sides
on such questions in the future.

I want to be sure I understood your lest letter about the symposium
expenses, Do you now hove permission to receive payment from us, as we
offered in ths first place, or will you gat payment direct. from the KIH?

S25 you tell me just what ly the technical problem in the estimation
of the apimerase of the Gal; mutant?

AS ever, yours cordially,

Jophua Igderberg
Professor of Medicul Genetics

JL few