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Published November 1, 1947 | Published
Journal Article Open

Methionine synthesis in Neurospora. The isolation of cystathionine


Among artificially produced biochemical mutants of Neurospora, those which have lost the ability to synthesize methionine form the largest class. At the present writing 87 occurrences of the methionineless character have been observed in this laboratory following treatment of wild type spores with high frequency radiations (1) or mustard gas (2). Methionineless mutants differ from wild type Neurospora in that they fail to grow on a medium containing only sugar, inorganic salts, and biotin, but do grow if, in addition to these constituents, methionine is supplied. In many of the mutants failure of methionine synthesis results from a block in the reduction of sulfate, which, except for a trace of biotin, is the sole source of sulfur in the basal medium. These strains can utilize reduced forms of inorganic sulfur for growth, as well as methionine and other organic sulfur compounds. On the other hand, some of the mutants require organically bound sulfur for growth, an indication that in these strains the block in methionine synthesis comes at a later stage than sulfate reduction. Similar classes of methionine-requiring mutants have been reported in the mold Ophiostoma by Fries (3) and in Escherichia coli by Lampen et al. (4-6).

Additional Information

© 1947 American Society of Biological Chemists. Received for publication, August 12, 1947. I wish to thank Dr. A.J. Haagen-Smit and Dr. G. Oppenheimer for the microanalyses reported here. Valuable assistance was rendered to the author by Dr. Marguerite Fling and Dr. R. Phinney. Committee on Food Research of the Quartermaster Food and Container Institute for the Armed Forces. The opinions or conclusions contained in this report are those of the author. They are not to be construed as necessarily reflecting the views or indorsement of the War Department. This investigation wras also supported in part by the Nutrition Foundation, Inc.

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