Dr. David -4. Bonner, ,
Osborn Botanical Laboratory,

Yale University,

Rew Haven, Connecticut.

i

Dear Dave: —

- Iwas glad to hear that Landman has gotten so far in the purification of

_ Neurospora lactase. “hat's the latest on it? We haven't been so ambitious;

I haven't even given very mich thought to the posaibility, on purely a prior’
discourageuantse It's 2 little harder to collect a kilo of dry 7. coll than of
Heurospora, Fut it has turned out to be so easy to extract, with water from
celis dried over P,O,, that I may give a try at chromtographic separation, —
with ONPG as an ator. By the way, jomciu your letter of Febr. 24 mentioned
that you might be able to spure someONPG. Yur supplies aré Betting low, and I
would be grateful for any anount that you can cow ortably divert.

It would be interesting to domare sone of your purifisd Neurospora laetase
kinetically with our coli prens. Can you send some? I am sending along 100 mg.
active dry calls of Kel2 for younto piay with. The powder shoul: be triturated .
suspended in 10 ml water, and after shaking aecouple of hours, sedimented at
Ga. 3500 rpm: 20 mins to prepare the extracts You should got an activity of
about 102 u./al, a unlit being the amount of enzyme which spiits enough ONP from
excess ONPG in aewolume of 10 wl. to cause a deflaction of 20 ontical density |

‘units in the Coleman spectrophotometer. This 1s just a lab unit; somefias I'll
recalculate it xinatically.

I think we have found a different enzyme (not gust presence or absence) in ,
ane of the mitant-suppressor combinations. (Lac,- Supp, 4). It seeas to be dis-
tinguished from wild type by a éonpe ef 7.7 x ib-4, Compared with 1.3 x 19-4 -
for Lacyy . But I wouldn't put any heavy interpretations on this, You eantt
distinguish an enzyxs whose specificity has been “altered by a gene", from
. just another enzyme vhich does the same job. Lao,- does produce the "type"
galactosidase under cartain conditions, so one cin regard the dzter-nination
of the different K, as a one-gene affair (Suppyi-/#).

Tha heteroaygotes are no less puzzling than in November. A lot more Linkage
data, but it doegn't point to anything simpler than sone kind of aberration,
I have a paper in presa in PNA’, in which I expressed the fearful possibility
that the sace khnd of aberration might operate in the formation of "hormal®
prototrophs. Sut there are large discrepanoles &n the linkage relationships that
mitigate against this. Zelie has been single-celling the, ani confirms their
one-gell origin. His pedigrees so far haven't shown auch sore, but this seens
to be the mogt promising approash.

eet
Something else has come up that may amuse you, as it has diséracted me.
K-12 is lysogenic. The phage that it carries aymblotically, however,
has so far attacked only two coli straing that were obtained as "mitants"
from K-12. These mutants are probably merely cultures which have been
disinfected by ultra-violet light, and accordingly become susceptible.

They can be reinfacted to becoma lysogenic again. This has abso&htely
nothing whatever to do with recombination, but it does khve "plasmagens”
significance, as the symbiosis conditions, by “interforence" resistance

to two phages, pl9 and p20 that were picked from Madison and Chicago sewage
for this purpose, I have been surprised to hear the suggestion (revived from
the literature of 30 years ago) that the lysogenic phage is a sort of
ganete since it has a tail!

Any chance cf sesiag you in Detroit? or Cinnedianati?

Best regardsag