The non-octarepeat copper binding site of the prion protein is a key regulator of prion conversion.
The conversion of the prion protein (PrP(C)) into prions plays a key role in transmissible spongiform encephalopathies. Despite the importance for pathogenesis, the mechanism of prion formation has escaped detailed characterization due to the insoluble nature of prions. PrP(C) interacts with copper through octarepeat and non-octarepeat binding sites. Copper coordination to the non-octarepeat region has garnered interest due to the possibility that this interaction may impact prion conversion. We used X-ray absorption spectroscopy to study copper coordination at pH 5.5 and 7.0 in human PrP(C) constructs, either wild-type (WT) or carrying pathological mutations. We show that mutations and pH cause modifications of copper coordination in the non-octarepeat region. In the WT at pH 5.5, copper is anchored to His96 and His111, while at pH 7 it is coordinated by His111. Pathological point mutations alter the copper coordination at acidic conditions where the metal is anchored to His111. By using in vitro approaches, cell-based and computational techniques, we propose a model whereby PrP(C) coordinating copper with one His in the non-octarepeat region converts to prions at acidic condition. Thus, the non-octarepeat region may act as the long-sought-after prion switch, critical for disease onset and propagation.
Department of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste, Italy.|Structural Biology Group, European Synchrotron Radiation Facility (ESRF), Grenoble, France.
Gabriele
G
Giachin
Department of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste, Italy.
Phuong Thao
PT
Mai
Department of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste, Italy.
Thanh Hoa
TH
Tran
Department of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste, Italy.
Giulia
G
Salzano
Department of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste, Italy.
Federico
F
Benetti
Department of Chemistry, Sapienza University of Rome, Rome, Italy.
Valentina
V
Migliorati
Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Rome, Italy.
Alessandro
A
Arcovito
Department of Medicine, Public Health, Life and Environmental Science, University of L'Aquila, Coppito Aquila, Italy.
Stefano
S
Della Longa
Scuola Normale Superiore, Pisa, Italy.|Istituto Nazionale di Fisica Nucleare (INFN) sezione di Pisa, Pisa, Italy.
Giordano
G
Mancini
Department of Chemistry, Sapienza University of Rome, Rome, Italy.
Paola
P
D'Angelo
Department of Neuroscience, Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste, Italy.|ELETTRA - Sincrotrone Trieste S.C.p.A, Trieste, Italy.
Giuseppe
G
Legname
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001665:Binding Sites; D045744:Cell Line, Tumor; D017124:Conserved Sequence; D003300:Copper / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D011328:Prions / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012091:Repetitive Sequences, Nucleic Acid; D013329:Structure-Activity Relationship
D011328:Prions; D003300:Copper