February 22, 1973
Dear Kathy:
Congratulations on the Stone Award. I knew they couldn't resist a Texan.
In regard to H. influenzae Endo R we have purified RIII (A,E,K) enzyme by gradient elution from PC (it comes off late) followed by DEAE cellulose (it runs through at 0.01 M NaPO4 pH 7.4). We are still looking for RII (J,G) enzyme in what elutes from DEAE at about 0.05M NaCl (i.e. 4 + clot test). We have pieced the following together:
[DIAGRAM]
[NOTATION: Circles indicate direct proof, others are deduced. All partials have expected MW[?]
RII (J,G) = Ham's Endo R
RIII (A,E,K) corresponds to Methylase III (--> NA A)
We think this corresponds to Murray's sequence [FORMULA] for Endo R on lambda (?) DNA. Since Murray got 5' A's, this sequence suggests RIII makes a staggered break at arrows.
In regard to enzymes, we now have large amounts of E. coli with RTF2 or RTF1, and I am beginning to purify RII and Tom Kelly will purify RI. We have just gotten a new culture of H. aegyptius and I plan to grow a large batch soon.
Your work seems to be going very well. Detailed sequences should soon follow. In regard to your question about staying longer, I think you should stay another year since the work is reaching its peak, and g to Howard Green's laboratory thereafter. I wouldn't worry about the availability of jobs. With your accomplishments and background, you should not have trouble.
I have already sent the slides you asked for.
Best regard to Walter.
Sincerely,
Daniel Nathans