NATIONAL INSTITUTE OF GENETICS

YATA 1,111 MISIMA, SIZUOKA-KEN,

411 JAPAN
Y. Hirota Cable address: Genetics, Misima

May 13, 1977

Professor Joshua Lederberg
Department of Genetics

Medical Center, Stanford University
Stanford, California 94305

U. S. A,

Dear Joshua :

I am grateful to you for sending my M.S. to P.N.A.S. and
thank you very much for your kindness on this matter.

I am continuing this line of experiment, as follows. We searched
for the mutants defective in either one of the 6 penicillin
binding proteins, hoping to find real lethal targets of penicillin
which were the indispensable part of the machinery for cell growth
and division of E. coli, as you have worked out many years ago.

We succeeded to isolate all of such mutants from my mutant
collection, except a mutant lacking the band 5/6. The mutants
lacking in 1b arrested cell growth at 42° and those lacking in 2
showed an ovoid cell shape at 40° as Spratt artd Pardee described.
The mutants lacking in 3 formed multinucleated filamentous cells
at 40°, as Spratt speculated. No thermosensitive mutation
associated with the defect of the penicillin binding protein la
and 4, I tentatively conclude that the lethal targets of penicillin
are lb, 2, and 3. We are now studying the phenotypes of these
mutants, and interested in the enzyme activities associated with
these binding proteins. Also, we are constructing a series of
multiple-defect mutants leaving only one of bands; 1b, 2, and 3
(and 5/6) and lacking in all other binding proteins. These
strains can be useful for separating the binding protein in pure
by penicillin-affinity chromatography.

I am hoping to be able to report you the results in my
next letter, soon.

Sincerely yours,

/. 7
Le Ofer
Y. Hirota