Following mutagenesis of Saccharomyces cerevisiae and screening for growth in the presence of the heterocyclic boron-containing drug diazaborine, we identified 17 resistant mutants which could be divided into three complementation groups. From one complementation group we cloned two alleles of the gene AFG2, which we propose to rename DRG1, coding for a protein of the AAA-family of ATPases. In addition to the specialized forms of the Walker A and B boxes found in this family, the encoded protein contains a heptapeptide repeat characteristic of leucine zippers. Localization of the mutated residue from one resistant allele in the region of the heptapeptide repeat suggests that this motif may have physiological relevance. Protein Drg1p is related to AAA proteins involved in vesicle trafficking or membrane fusion, like Sec18p or Cdc48p. Our studies show that the mutant and wild-type alleles encode an 85 kDa soluble protein which can be expressed both in E. coli and yeasts. Presently, we are investigating the protein 92s cellular localization and determining if it plays a role in protein trafficking. The subcellular localization experiments show that the protein is associated with the 100.000 x g-pellet. Whether DRG1p is linked to ribosomes or is part of a vesicle sedimenting with the ribosomes cannot be decided at the moment. We have obtained a temperature sensitive yeast mutant which is defective in this gene. This mutant stops growth at the non permissive temperature and shows an unusually large cell size and big vacuoles.