title: Suppression of acetate mutants in Coprinus : II. Correlation of recessiveness and dosage effects with suppressed enzyme level.
abstract: Recessiveness and dosage effects of two suppressor genes in Coprinus were correlated with suppressed enzyme activity in cell free extracts. Wild type, the suppressible acu-1.4 mutation and suppressor gene mutations supa4.1(+) and supa4.2(+) were used to construct appropriate diploid strains which allowed comparison of the following situations: (i) wild type, (ii) unsuppressed mutant (iii) homoallelism for a single suppressor, (iv) heterozygosity for a single suppressor (sup (+)/sup (-)) and (v)heterozygosity for two nonallelic suppressors. Extracts of the unsuppressed mutant had no enzyme activity whereas extracts of both the homoallelic suppressor strains had the suppressed level of some 20% wild type acetyl-CoA synthetase activity. Diploids heterozygous for sup (+)/sup (-) were acu(-) in phenotype. These had only 3-6% wild type enzyme activity, a level too low to support growth on acetate and hence the apparent recessiveness of each sup (+) mutation. The doubly heterozygous diploid had exactly the same level of enzyme activity as homoallelic diploids, 20% wild type, hence the acu (+) suppressed phenotype.
authors.affiliation: School of Biological Sciences, Queen Mary College, Mile End Road, El 4NS, London, England.
authors.forename: K H
authors.initials: KH
authors.lastname: Vousden
authors.forename: L A
authors.initials: LA
authors.lastname: Casselton