N-Terminal Segment of Tv CyP2 Cyclophilin from Trichomonas vaginalis Is Involved in Self-Association, Membrane Interaction, and Subcellular Localization.

In Trichomonas vaginalis ( T. vaginalis ), cyclophilins play a vital role in dislodging Myb proteins from the membrane compartment and leading them to nuclear translocation. We previously reported that Tv CyP1 cyclophilin from T. vaginalis forms a dimer and plays an essential role in moving the Myb1 transcription factor toward the nucleus. In comparison, Tv CyP2 containing an extended segment at the N-terminus (N-terminal segment) formed a monomer and showed a different role in regulating protein trafficking. Four X-ray structures of Tv CyP2 were determined under various conditions, all showing the N-terminal segment interacting with the active site of a neighboring Tv CyP2, an unusual interaction. NMR study revealed that this particular interaction exists in solution as well and also the N-terminal segment seems to interact with the membrane. In vivo study of Tv CyP2 and Tv CyP2-∆N ( Tv CyP2 without the N-terminal segment) indicated that both proteins have different subcellular localization. Together, the structural and functional characteristics at the N-terminal segment offer valuable information for insights into the mechanism of how Tv CyP2 regulates protein trafficking, which may be applied in drug development to prevent pathogenesis and disease progression in T. vaginalis infection.