The Nitric Oxide story with Larry Keefer: Mutagenicity of Nitric
Oxide (NO)
Working with Tom Cebula and Walter Koch at FDA/CFSAN, we determined the
nature of the mutations induced by Larry Keefer’s nitric-oxide donating
agents in Salmonella bacteria, using Walter’s method of
oligonucleotide hybridization. NO donors were positive in strain TA 1535
(HisG 46 GGG triplet target). This was the first detection of NO,
a newly discovered agent found as a major player in many biological
processes, as a mutagen. Larry was creating NO donor agents as models
for study and as potential cancer chemotherapeutics. TA1535 is also the
target strain for N-Nitroso compounds like MNU and MNNG. Nitric oxide
and nitroso compounds are not related chemically, but may seem formally
similar with an “N-O” group in each. Targeting the sameSalmonella genetic target led to the obvious question - whether
NO mutagenesis was mechanistically similar to N-nitroso compound
mutagenesis. Our experiments with oligonucleotide hybridization showed
that the sequence changes resulting from NO and nitroso compound
mutagenesis were not the same. One targeted the first G in the triplet,
while the other targeted the second G in the triplet (the third
position, “wobble” is not selected when altered). Thus, the mechanisms
were different. What a delightful result! This data led to another paper
in Science (Wink et al.,1991) that I had spent a lot of time editing
before submission, in order to get the context right. I had submitted
the Gilvocarcin paper first to Nature and they returned it without
review. I thought hard and re-wrote it, working on the context
especially, before submitting to Science, where it was accepted without
revision. [Batting average: Science: 1000, PNAS: 0]