Fig. 5. The C-terminal region of Drs2p is essential for its function. (A) Sequence alignment of the entire C-terminal cytoplasmic region of Saccharomyces cerevisiae (Sc) Drs2p (accession number NP_009376) and its homologues from Ajellomyces capsulatus (accession number AAF90186) and Schizosaccharomyces pombe (accession number NP_596486). Also shown is an alignment of a region conserved between mammalian and yeast ATPases. (B) C-terminal truncations and internal deletions of Drs2p were transformed into SEY6210 drs2::TRP1, and ability to grow at 20°C was determined. Truncations or deletion mutants that failed to grow at 20°C were transformed with multicopy plasmids carrying GEA1 and GEA2, and growth was monitored at 20°C. In each case, overexpression of either Gea1p or Gea2p partially suppressed the growth defect. Hatched box, Gea2p interaction region; black box, highly conserved region; underlined, NPFXD motifs. (C) SEY6210 drs2::TRP1 was co-transformed with low-copy centromeric plasmids carrying drs2-D560N and the C-terminal truncation mutant drs21246-1355 (lower panel), and appropriate vector controls (upper panel). Some variability in the level of growth of the four independently isolated drs2-D560N + drs21246-1355 co-transformants at the non-permissive temperature was noted, but in all cases significant growth, compared to a drs2 strain, was evident.