FIG. 3.
Pex18p and Pex21p contact Pex13p and Pex14p only in the presence of Pex7p. (A) Confinement of the Pex13p-binding region for Pex7p, Pex18p, and Pex21p. The indicated fragments of Pex13p were tested in a two-hybrid assay for interaction with Pex7p, Pex18p, and Pex21p in the HF7c wild-type strain. (B) Dependence of the Pex13p1-100 interactions with Pex7p, Pex18p, and Pex21p on endogenous PEX7 and PEX18/PEX21. The assays with Pex13p1-100 were repeated in the otherwise isogenic HF7c strains pex7Δ and pex18Δ pex21Δ. Histidine prototrophs were not observed for Pex18p/Pex21p in the absence of Pex7p. (C) Dependence of the Pex7p-Pex14p two-hybrid interaction on endogenous PEX18/PEX21. The respective Pex7p and Pex14p fusions were transformed into HF7c and the corresponding pex18Δ pex21Δ strain. In both strains, coexpression of Pex7p and Pex14p caused growth on histidine dropout plates.