โ Scribed by Werner K. Maas
No coin nor oath required. For personal study only.
The present account spans the history of arginine regulation from its discovery in 1955 until the present. In 1957 I demonstrated that not only added arginine but also internally produced arginine represses enzyme formation and that the potential for enzyme synthesis is in excess of what is required for growth. In 1959 I located the regulatory gene argR encoding the arginine repressor. An unusual feature of this research was the finding that in E. coli B, in contrast to E. coli K12, arginine synthesis is permanently repressed, independent of arginine. This was due to a single amino acid difference between the two repressors. Recent studies showed that, in natural populations of E. coli, K12โtype regulation is much more frequent than Bโtype regulation, and that E. coli B evolved from a strain with K12โtype regulation. In competition experiments, __E. coli K1__2 was found to be favored in the presence of arginine and E. coli B in its absence, showing that contrary to expectations permanently turned off regulation is favored over negative regulation in some environments. BioEssays 29:484โ488, 2007. ยฉ 2007 Wiley Periodicals, Inc.
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