MUTATIONAL SPECIFICITY OF THE FERROUS ION IN A SUPF GENE OF ESCHERICHIA-COLI

A plasmid, pZ189, was treated with Fe2+/EDTA, and mutagenesis was determined by DNA sequencing. In the fgp(+) Escherichia coli host, 78% were base substitutions, with G:C->C:G transversion (58.7%) predominant, followed by G:C->T:A transversion (28.3%). In the fpg-1 mutant, 88% were base substitutions among which 46% were G:C->C:G and 42% G:C->T:A. Fe2+ resulted in increased formation of 8-hydroxydeoxyguanosine (8-ohdG) in pZ189 DNA. The origin of Fe2+-induced G:C->T:A transversion may be 8-ohdG; on the other hand, the origin of G:C->C:G is neither 8-ohdG nor 2,6-diamino-4-hydroxy-5-formamidopyrimidine. (C) 1995 Academic Press, Inc.