| Popis: |
Soon after 1944, Jacques Monod organized informal meetings at which Monod and the author presented their work, subjecting it to the criticism of all the attendants. During 1948, the author and Marie-Louise Hirsch observed that the growth of a leucine-requiring mutant of Escherichia coli was inhibited by valine or isoleucine, whereas its growth on leucylglycine or glycylleucine was unaffected by the antagonists. In the discussion of the paper, one of the hypotheses put forward was the existence of a selective permeation system in E. coli, stereo-specific for the three branched-chain amino acids. Jacques struck out the corresponding paragraph with a choleric red pencil and told the author, "Every time a microbiologist has no clear explanation for a nutritional puzzle, he calls upon permeability to conceal his ignorance." The paper appeared in 1953 with alternative explanations, which turned out to be entirely wrong. The fact that more than one activity is controlled by the same pleiotropic mutation did in an indirect manner help the development of the operon concept. The author says that people have recalled how Jacques' lab was associated with the discovery of the repression of biosynthetic enzymes by their end products and with the generalization of the negative-regulation model in biosynthetic systems, and some others have described the rationale by which Jacques arrived at the concept of allosteric enzymes. |
