The yeast gene SNQ2 confers hyper-resistance to the mutagens 4-nitroquinoline-N-oxide (4-NQO) and Triaziquone, as well as to the chemicals sulphomethuron methyl and phenanthroline when present in multiple copies in transformants of Saccharomyces cerevisiae. Subcloning and sequencing of a 5.5 kb yeast DNA fragment revealed that SNQ2 has an open reading frame of 4.5 kb. The putative encoded polypeptide of 1501 amino acids has a predicted molecular weight of 169 kDa and has several hydrophobic regions. Northern analysis showed a transcript of 5.5 kb. Haploid cells with a disrupted SNQ2 reading frame are viable. The SNQ2-encoded protein has domains believed to be involved in ATP binding and is likely to be membrane associated. It most probably serves as an ATP-dependent permease.