FIG. 7.

Point mutations in the Walker A and B domains disrupt growth. (A) Selected residues in Walker domains A and B of Rvb2p were substituted by site-directed mutagenesis. (B) Point mutations G80A and K81A (Walker A motif) cause temperature-sensitive growth defects. Left plate, permissive temperature (30°C); right plate, restrictive temperature (37°C). (C) The D296N allele is lethal and also toxic when overexpressed in a wild-type background. Growth of a wild-type strain (MH2-h) expressing a high-copy-number GAL1::rvb2 D296N allele is severely impaired in galactose medium (right, bottom two rows) but unaffected when expression is repressed by incubation in glucose (left, bottom two rows). No effects occur with the empty vector (left and right, top rows) or a vector containing a wild-type RVB2 allele under the control of the GAL1 promoter (left and right, second rows from top). The dilution series is indicated above each panel. N, no dilution.