Human pancreatitis-associated protein forms fibrillar aggregates with a native-like conformation.
Human pancreatitis-associated protein was identified in pathognomonic lesions of Alzheimer disease, a disease characterized by the presence of filamentous protein aggregates. Here, we showed that at physiological pH, human pancreatitis-associated protein forms non-Congo Red-binding, proteinase K-resistant fibrillar aggregates with diameters from 6 up to as large as 68 nm. Interestingly, circular dichroism and Fourier transform infrared spectra showed that, unlike typical amyloid fibrils, which have a cross-beta-sheet structure, these aggregates have a very similar secondary structure to that of the native protein, which is composed of two alpha-helices and eight beta-strands, as determined by NMR techniques. Surface structure analysis showed that the positively charged and negatively charged residues were clustered on opposite sides, and strong electrostatic interactions between molecules were therefore very likely, which was confirmed by cross-linking experiments. In addition, several hydrophobic residues were found to constitute a continuous hydrophobic surface. These results and protein aggregation prediction using the TANGO algorithm led us to synthesize peptide Thr(84) to Ser(116), which, very interestingly, was found to form amyloid-like fibrils with a cross-beta structure. Thus, our data suggested that human pancreatitis-associated protein fibrillization is initiated by protein aggregation primarily because of electrostatic interactions, and the loop from residues 84 to 116 may play an important role in the formation of fibrillar aggregates with a native-like conformation.
Ho
Meng-Ru
MR
Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.
Lou
Yuan-Chao
YC
Lin
Wen-Chang
WC
Lyu
Ping-Chiang
PC
Huang
Wei-Ning
WN
Chen
Chinpan
C
D000595:Amino Acid Sequence; D000951:Antigens, Neoplasm / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D014408:Biomarkers, Tumor / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002942:Circular Dichroism; D003224:Congo Red; D006801:Humans; D006863:Hydrogen-Ion Concentration; D037181:Lectins, C-Type / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D009682:Magnetic Resonance Spectroscopy; D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D008969:Molecular Sequence Data; D000073718:Pancreatitis-Associated Proteins; D011494:Protein Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012995:Solubility; D040681:Structural Homology, Protein
D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D037181:Lectins, C-Type; D000073718:Pancreatitis-Associated Proteins; C000612141:REG3A protein, human; D003224:Congo Red; D011494:Protein Kinases