A NOVEL PLANT PEPTIDYL-PROLYL-CIS-TRANS-ISOMERASE (PPIASE) - CDNA CLONING, STRUCTURAL-ANALYSIS, ENZYMATIC-ACTIVITY AND EXPRESSION

A novel cDNA encoding for a peptidyl-prolyl-cis-trans-isomerase (PPIas e) belonging to the FK506-binding protein (FKBP) family was isolated f rom wheat. It contains an open reading frame of 559 amino acids and it represents the first plant FKBP-PPIase to be cloned. It possesses a u nique sequence which is composed of three FKPB-like domains, in additi on to a putative tetratricopeptide repeat (TPR) motif and a calmodulin -binding site. The recombinant FKBP-PPIase expressed in and purified f rom Escherichia coli exhibits PPIase activity that is efficiently inhi bited by the immunosuppressive drugs FK506 and rapamycin. Northern blo t analysis showed that wheat FKBP was found mainly in young tissues. P olyclonal antibodies revealed the presence of cross-reacting proteins in embryos, roots and shoots. The unique structural features, the enzy matic activity and the presence of putative isoforms in wheat tissues indicate the possibility of the involvement of wheat PPIase in essenti al biological functions, similar to other members of the FKBP gene fam ily.