Solution structure of the human parvulin-like peptidyl prolyl cis/trans isomerase, hPar14

The hPar14 protein is a peptidyl prolyl cis/trans isomerase and is a human parvulin homologue. The hPar14 protein shows about 30% sequence identity wi th the other human parvulin homologue, hPin1. Here, the solution structure of hPar14 was determined by nuclear magnetic resonance spectroscopy. The N- terminal 35 residues preceding the peptidyl prolyl isomerase domain of hPar 14 are unstructured, whereas hPin1 possesses the WW domain at its N terminu s. The fold of residues 36-131 of hPar14, which comprises a four-stranded b eta -sheet and three alpha -helices, is superimposable onto that of the pep tidyl prolyl isomerase domain of hPin1. To investigate the interaction of h Par14 with a substrate, the backbone chemical-shift changes of hPar14 were monitored during titration with a tetra peptide. Met90, Val91, and Phe94 ar ound the N terminus of alpha3 showed large chemical-shift changes. These re sidues form a hydrophobic patch on the molecular surface of hPar14. Two of these residues are conserved and have been shown to interact with the proli ne residue of the substrate in hPin1. On the other hand, hPar14 lacks the h Pin1 positively charged residues (Lys63, Arg68, and Arg69), which determine the substrate specificity of hPinl by interacting with phosphorylated Ser or Thr preceding the substrate Pro, and exhibits a different structure in t he corresponding region. Therefore, the mechanism determining the substrate specificity seems to be different between hPar14 and hPin1. (C) 2001 Acade mic Press.