Genetic and Biochemical Studies of the Cystine-Methionine Series of Mutants in Neurospora crassa

NOTE: Text or symbols not renderale in plain ASCII are indicated by [...]. Abstract is included in .pdf document. 1. The following enzyme activities were studied in extracts of wild type and mutant Neurospora: [...]. Activity 2 was shown to be absent in a homocysteineless mutant and activity 3 was shown to be absent in a cystathionineless mutant. It was found that a suppressor, obtained by Giles, which causes these mutants to grow on minimal, returns enzyme activity to the mutants. Each activity is shown to be catalyzed by a different enzyme. 2. Evidence is presented which indicates that a Neurospora cystathionineless mutant can synthesize cystathionine from methionine without the intervention of cysteine. 3. Mutants which are blocked between thiosulfate and cysteine are shown to grow on elemental sulfur and H[subscript 2]S