Nonspecific prion protein-nucleic acid interactions lead to different aggregates and cytotoxic species.

A misfolded form of the prion protein (PrP) is the primary culprit in mammalian prion diseases. It has been shown that nucleic acids catalyze the misfolding of cellular PrP into a scrapie-like conformer. It has also been observed that the interaction of PrP with nucleic acids is nonspecific and that the complex can be toxic to cultured cells.

An aggregation-prone intermediate species is present in the unfolding pathway of the monomeric portal protein of bacteriophage P22: implications for portal assembly.

The head of the P22 bacteriophage is interrupted by a unique dodecameric portal vertex that serves as a conduit for the entrance and exit of the DNA. Here, the in vitro unfolding/refolding processes of the portal protein of P22 were investigated at different temperatures (1, 25, and 37 degrees C) through the use of urea and high hydrostatic pressure (HHP) combined with spectroscopic techniques. We have characterized an intermediate species, IU, which forms at 25 degrees C during unfolding or refolding of the portal protein in 2-4 M urea.

Ca(2+) and Mg(2+) binding to weak sites of TnC C-domain induces exposure of a large hydrophobic surface that leads to loss of TnC from the thin filament.

The C-domain of troponin C, the Ca(2+)-binding subunit of the troponin complex, has two high-affinity sites for Ca(2+) that also bind Mg(2+) (Ca(2+)/Mg(2+) sites), whereas the N-domain has two low-affinity sites for Ca(2+). Two more sites that bind Mg(2+) with very low affinity (K(a)<10(3)M(-1)) have been detected by several laboratories but have not been localized or studied in any detail. Here we investigated the effects of Ca(2+) and Mg(2+) binding to isolated C-domain, focusing primarily on low-affinity sites.