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]