Structural Analysis of the 42 kDa Parvulin of .

is a unicellular eukaryotic parasite, which causes the African sleeping sickness in humans. The recently discovered trypanosomal protein Parvulin 42 (Par42) plays a key role in parasite cell proliferation. Homologues of this two-domain protein are exclusively found in protozoa species. Par42 exhibits an N-terminal forkhead associated (FHA)-domain and a peptidyl-prolyl--isomerase (PPIase) domain, both connected by a linker. Using NMR and X-ray analysis as well as activity assays, we report on the structures of the single domains of Par42, discuss their intra-molecular interplay, and give some initial hints as to potential cellular functions of the protein.