Mutations affecting cysteine synthesis in Aspergillus nidulans: characterization and chromosome mapping

Abstract
Selection and mapping of mutations affecting cysteine synthesis in Aspergillus nidulans was carried out. A new locus, cysE, is described, the mutants of which are deficient in in vivo conversion of O-acetylserine to cysteine, a step mediated by cysteine synthase. Three loci (cysB, C and E) were thus found to control this step in vivo, apparently without affecting the enzyme activity in vitro. By scoring for propargylglycine sensitivity of cys mutants, chromosomal map positions were obtained for all five cysteine loci (A, B, C, D and E).