Studies on Wheat Prolyl Isomerase in Transgenic Plants

Abstract

Peptidyl prolyl isomerases catalyse the interconversion between cis and trans forms of the peptide bond preceding proline residues in proteins. Three distinct families of prolyl isomerases have been identified: the cyclophilins, the FKBPs and the parvulins (Schmid 1997; Dolinski, Heitman 1997). Cyclophilins and FKBPs have attracted attention as the cellular receptors for the immunosuppresants cyclosporin A, FK506 and rapamycin, but this role in drug action is distinct from the enzymatic activity. Members of the three prolyl isomerase families are highly conserved, abundant and expressed in multiple cellular compartments, suggesting that these enzymes play a critical role in cell physiology. Because prolyl isomerases can accelerate slow protein refolding steps in vitro, it has been speculated that this is what they do in vivo. A number of proteins physically associated with different prolyl isomerases such as kinases and transcription factors have been identified but the physiological significance of these associations remains to be established. The prolyl isomerases have been implicated in various cellular functions (independent of their prolyl isomerase activity) such as DNA degradation activity and RNA maturation.