“…Full-length CAX1 and CAX3 and N-terminal truncated sCAX1 and sCAX3, both lacking the first 36 amino acids, were used from previous studies (13,17,25). Full-length CAX1 point mutants (CAX1-S10A, CAX1-S25A, CAX1-S25T, CAX1-S25D, CAX1-E7A/E13A, and CAX1-R26A/E27A) and sCAX1/sCAX3 chimeras (sCAX1-␣ and sCAX3-␣1) were constructed in previous studies (14,16,17). Yeast strain K667 expressing wild-type CAX1, CAX1 mutants, or sCAX1/sCAX3 chimeras, which are hypersensitive to high concentrations of Ca 2ϩ , were transformed with SOS2 (7) or SOS2 variants (18), which were cloned into the yeast expression vector p2UGpd (19).…”