Preliminary results of human PrPC protein studied by spectroscopic techniques

Highlights: • First attempt of XAS study of lyophilized PrP^C-Cu(II) complex was successfully made. • Complementary, AFM has shown that PrP^C main domain has around 5 nm in diameter. • A protocol of fixing PrP^C sample on solid substrate was developed for further study. • By using ab-initio calculations, structures of PrP^C-Cu(II) binding site were proposed. • The LCF has shown two coexisting Cu(II) binding modes in sample: 4N and 3N + 2O. Neurodegenerative diseases are one of the malfunctions of human nervous system, being a class of complex and prominent pathologies. The human prion Protease Resistant Protein (PrP) is protein regulating copper metabolism in mammalian cells through binding of Cu(II) ions to specific fragments. Nowadays misfolding of this protein is associated with development of prion diseases. Therefore, it is crucial to obtain structural information about coordination of Cu(II) by PrP protein. Herein, we report X-ray absorption spectroscopy (XAS) measurements, carried out on SuperXAS beamline (SLS, PSI Villigen) on PrP^C-Cu(II) complexes. Obtained results were compared with theoretical predictions done by FEFF 9.6 software. Complementary to XAS data, Atomic Force Microscopy (AFM) measurements were conducted to obtain low resolution structural information about prepared sample that allow to develop protocol of fixing PrP^C molecules on solid substrate used for further experiments. It has been established that folded C-terminal domain of PrP^C protein has around 5 nm in diameter. Presented results showed that both XAS and AFM methods are useful tools in detailed examination of complexes of human PrP^C either with Cu(II) or with other divalent metal ions.