The amino acid analogues p-fluorophenylalanine (PFP) and ethionine (ETH) are strongly mutagenic in Coprinus lagopus. The most pronounced effect was found with suppressor mutations of the met-1 locus. PFP, at a concentration of 2·4 × 10−4 M, increased the mutation frequency 500 fold and ETH, at a concentration of 2·4 × 10−3 M, 30 fold over the spontaneous mutation frequency. From the spectrum of suppressors of the met-1 locus and the dominant revertants of the ad-82 locus, induced by analogue treatments, it was concluded that both analogues induce single base-change mutations. The dose response curves follow a sigmoid plot, revealing that within a certain range of analogue concentrations, muta-genesis is strongly dose dependent.
Using analogue resistant mutants, it has been shown that PFP mutagenesis is a function of its incorporation into protein. However, ETH mutagenesis is independent of protein incorporation but can be correlated with the degree of ethylation of nucleic acids. The synergistic effect PFP and ETH supports the evidence of the different mutagenic actions of the two analogues.