PURIFICATION OF FKBP-70, A NOVEL IMMUNOPHILIN FROM SACCHAROMYCES-CEREVISIAE, AND CLONING OF ITS STRUCTURAL GENE, FPR3

A novel protein, belonging to the yeast family of FKBPs (FK-binding pr oteins), FKBP-70, was isolated from Saccharomyces cerevisiae by its in teraction with the immunosuppressive agent FK-520. Its structural gene , FPR3, was cloned and the protein expressed and purified from Escheri chia coli. This third member of the FKBP family in yeast is homologous to the other FKBPs at its carboxy terminus, showing conserved ligand binding and proline isomerase regions. It is, however, a longer acidic protein with several potential nuclear targeting sequences and a regi on of homology to nucleolins. Yeast strains deleted for FPR3, as well as a triple deletion mutant of this family of genes, FPR1, FPR2 and FP R3, are viable under normal conditions of growth, indicating that the FPR genes are not essential for life.