NMR solution structure of hPar14 reveals similarity to the peptidyl prolylcis/trans isomerase domain of the mitotic regulator hPin1 but indicates a different functionality of the protein

The 131-amino acid residue parvulin-like human peptidyl-prolyl cis/trans is omerase (PPIase) hPar14 was shown to exhibit sequence similarity to the reg ulator enzyme for cell cycle transitions human hPin1, but specificity for c atalyzing pSer(Thr)-Pro cis/trans isomerizations was lacking. To determine the solution structure of hPar14 the H-1, C-13, and N-15 chemical shifts of this protein have been assigned using heteronuclear two and three-dimensio nal NMR experiments on unlabeled and uniformly N-15/C-13-labeled recombinan t protein isolated from Escherichia coli cells that overexpress the protein . The chemical shift assignments were used to interpret the NOE data, which resulted in a total of 1042 NOE restraints. The NOE restraints were used a long with 71 dihedral angle restraints and 38 hydrogen bonding restraints t o produce 50 low-energy structures. The hPar14 folds into a beta alpha(3)be ta alpha beta(2) structure, and contains an unstructured 35-amino acid basi c tail N-terminal to the catalytic core that replaces the WW domain of hPin 1 homologs. The three-dimensional structures of hPar14 and the PPIase domai n of human hPin1 reveal a high degree of conservation. The root-mean-square deviations of the mean atomic coordinates of the heavy atoms of the backbo ne between residues 38 to 435, 50 to 58, 64 to 70, 81 to 86, 115 to 119 and 122 to 128 of hPar14 were 0.81(+/-0.07) Angstrom. The hPar14 model structu re provides insight into how this class of PPIases may select preferential secondary catalytic sites, and also allows identification of a putative DNA -binding motif in parvulin-like PPIases. (C) 2000 Academic Press.