Cloning, expression and characterisation of FKB-6, the sole large TPR-containing immunophilin from C. elegans

We have cloned, expressed, purified and characterised ceFKB-6, the only large tetratricopeptide repeat motif-containing immunophilin in Caenorhabditis elegans which is similar to the human orthologues FKBP51 and FKBP52. It shows increased peptidyl prolyl isomerase activity, the measured kcat/Km of 1.3 × 106 M−1 s−1is twofold greater than that of hFKBP12 and hFKBP51. NMR studies of the interaction between FKB-6 and the C-terminal DAF-21 pentapeptide MEEVD show interactions consistent with those found between the large human immunophilin TPR domains and human Hsp90. In vivo localisation studies show that the fkb-6 gene is expressed in all stages from embryo to adult with predominant expression being noted in the adult dorsal and ventral nerve cords.