Structural Characterization of the Intra- and Inter-Repeat Copper Binding Modes within the N-Terminal Region of “Prion Related Protein” (PrP-rel-2) of Zebrafish

Abstract

The unique biology of prion proteins (PrPs) allied with the public-health risks posed by prion zoonoses, such as various animal neurodegenerations, has focused much attention on the molecular basis of the controls cross-species and on the similarities between PrPs from different species. Given the common feature of PrPs as Cu(2+) binding proteins, it appears relevant to compare the impact of Cu(2+) on the stability constants and structures of "physiological" complexes. After having comprehensively delineated the interaction of Cu(2+) with mammalian and avian PrPs, the stabilities and molecular structures of species generated by Cu(2+) interacting with the irregular repeated domain derived from Danio rerio zebrafish PrP-rel-2 were investigated. Copper complexes with different zebrafish PrP-rel-2 fragments were analyzed by potentiometric and spectroscopic techniques. The data were interpreted as to provide evidence of all investigated repeat units selectively binding Cu(2+) via the His imidazole(s). The structural models obtained from paramagnetic NMR showed an intra- or inter-copper binding according to the number of the His in the sequence. In comparison to the mammalian and avian cases, the enzymatic function referred to SOD-like activity was shown to be rather faint in the fish PrPs cases.

Cu2+ and Ni2+ interactions with N-terminal fragments of Hpn and Hpn-like proteins from Helicobacter pylori

“…log β logK UV-Vis CD EPR pH derived from the involvement of the amide nitrogen in the metal ion binding { N -, 2N im } [30], but this is fast overlapped with CuL and CuH -2 L species. We can describe the CuH -2 L complex which exists in pH range 7-10 ( Fig.…”

“…The involvement of imidazole and amide nitrogens is confirmed by characteristic charge transfer transitions detected in CD spectra: N im → Cu 2+ at about 255 nm and N -→ Cu 2+ CT band at 299 nm. The formation of the CuH -3 L complex (with logK 9.28) does not significantly affect the pattern of the CD spectra although the mixed N im → Cu 2+ and N − → Cu 2+ charge transfer (CT) transition appears at 322 nm [27,30]. The strong shift from 578 nm to 522 nm in absorption band and changes in EPR parameters may be consistent with the participation of an additional amide nitrogen in the coordination sphere which replaces one of the imidazole nitrogens resulting in {3N − , N im } coordination.…”

Copper binding to chicken and human prion protein amylodogenic regions: Differences and similarities revealed by Ni2+ as a diamagnetic probe

“…Up to four Cu 2+ ions are bound within the so called ''octarepeat region" (residues 60-91) [14][15][16][17][18][19][20][21][22][23][24], and two additional ions can be bound by His residues (His-96 and His-111) outside the tandem repeat region, in the so called ''amyloidogenic" region (residues 91-126) [25][26][27][28][29][30][31][32][33]. Prion or prion-like proteins of species different from mammals showed very similar copper binding to the N-terminal tandem repeat region [34][35][36][37][38][39][40][41][42][43][44].…”

Evolutionary Implications of Metal Binding Features in Different Species’ Prion Protein: An Inorganic Point of View

“…These Gly-rich peptides form metal complexes at pH = 7.4 in which the copper(II) is bound to two imidazole and two amide nitrogen atoms (2N Im , 2N − ) or form inter-repeat binding, involving three imidazole nitrogen atoms [80,81,82]. The sequence of the fish prion N-terminal domain is more different from that of mammals, whereas analogous avian prion domain shows more similarity.…”