Biology subjects

Martin-Pastor, M.

Publications and source records attributed to Martin-Pastor, M..

4 recordsLinked to original sources

bioRxiv2026

Unfolding of the disease-linked bank vole prion protein E200K in the context of PrPSc propagation

The elucidation of the atomistic structure of PrPSc has, disappointingly, not revealed the mechanism underlying prion propagation. This is because PrPSc has been shown to be a standard amyloid, and as such, it can only template a polypeptide chain that is unfolded. Therefore, while PrPSc can easily template the disordered ~90-120 domain of an incoming PrPC molecule, it does not have any obvious capacity to template its ~121-231 folded domain (FD). The FD needs to accommodate into the ~121-230 PrPSc surface, an inert "Procrustean bed". We have recently proposed that unfolding of the FD is a prerequisite for its conversion to the PrPSc conformation and using experimental and computational methods identified the likely early events of such process using bank vole (BV)PrP(90-231) as our working model. We concluded that a key early event is the destabilization of the short {beta}1-{beta}2 assembly, and that the segment contiguous to the disordered tail, ~121-140, encompassing {beta}1 and its adjacent coils, is the most likely region to unfold first. In the present study we applied the same methodology to the disease-related PrP mutant E200K. E200K is the most prevalent mutation leading to familial prion disease in humans, yet the stability of its FD is only marginally lower compared to that of the protein with the wild type (wt) sequence. We, therefore, aimed at assessing whether the early unfolding events of BVPrPC(E200K) are similar or different to those of wtBVPrPC and whether such early unfolding route might provide insight into the extreme capacity of PrPC(E200K) to spontaneously generate PrPSc. It should be noted that generation and propagation of PrPSc are distinct phenomena, even though both are mechanistically related and dependent on conformational changes in PrPC. Our data show that early unfolding events of BVPrPC(E200K) are essentially similar to those of wt BVPrPC. However, interesting nuances exist.

biochemistry↗

bioRxiv2025

Unfold to refold: Tracking the initial steps of PrPC unfolding in the context of PrPSc propagation

It might have been believed that elucidation of the atomistic structure of PrPSc would lead to an immediate understanding of the mechanism of prion propagation. However, PrPSc, now known to be a "simple" amyloid, can just template a previously unfolded polypeptide chain. Therefore, PrPSc can easily template the disordered [~]90-120 domain of an incoming PrPC molecule, but not its [~]121-231 folded domain (FD). The FD needs to accommodate into the [~]121-230 PrPSc surface, an inert "procrustean bed". Thus, a mechanism for concerted unfolding/refolding of the FD must exist, with FD unfolding as a key element. To explore how this might happen, we performed thermal unfolding of recombinant bank vole PrPC(90-231), that is a universal PrPSc propagator PrPSc, tracking changes at the residue level with solution NMR to pinpoint early unfolding propensity. Our data suggest that a key early event is the destabilization of the short {beta}1-{beta}2 assembly, and that the segment contiguous to the disordered tail, [~]121-140, encompassing {beta}1 and its adjacent coils, is the most likely region to unfold first. Spectroscopic data obtained at higher temperatures suggest that portions of alpha helix 2 are likely the last elements of the FD to unfold and refold into the PrPSc conformation. Molecular Dynamics simulations assisted the interpretation of these changes and suggest separation of 1 from the rest of the FD ensemble. Our data provide a conceivable timeline of the early events in PrPSc-assisted conversion of PrPC and should serve as a starting framework to develop a future atomistic model of PrPSc propagation.

biochemistry↗

bioRxiv2021

Solid state NMR reveals a parallel in register architecture for an infectious recombinant prion

Two alternative architectures have been proposed for PrPSc, the most notorious prion: a parallel in register {beta} stack (PIRIBS) and a 4-rung {beta}-solenoid (4R{beta}S). We challenged these two models by measuring intermolecular 13C-13C dipole-dipole couplings of 13CO-labelled Phe residues in a fully infectious sample of recombinant bank vole PrPSc (recBVPrPSc) using a PITHIRDS-CT solid state NMR (ssNMR) experiment. To our surprise, data strongly support a PIRIBS architecture. However, the mean distance measured ([~]6.5 [A]) suggests that a minimum of two of the three Phe residues are not perfectly stacked at the canonical [~]5 [A] cross-{beta} distance. Additional ssNMR experiments show some local conformational variability of the Phe residues within limits of a relatively high rigidity. The most parsimonious interpretation of our data is that recBVPrPSc is arranged as a PIRIBS, although additional conformers with alternative architectures cannot be excluded, including a mixture of PIRIBS and 4R{beta}S. Author summaryPrPSc is the most notorious prion. It is an infectious protein that cuases fatal neurodegenerative diseases in humans and animals. PrPSc is the aberrant version of a brain protein, PrPC. PrPSc and PrPC have the same prinary structure, but different secondary, tertiaty and quaternary structures. PrPSc is capable of templating PrPC to convert to the PrPSc conformation, which is the basis of its capacity to propagate. Two plausible structural models of PrPSc have been proposed, the four-rung {beta}-solenoid (4R{beta}S) and the parallel in-register {beta} stack (PIRIBS) model. In both cases the driving force of the templating mechanism consists of "sticky" surface {beta}-strands; however, in the PIRIBS model all the {beta}-strands that conform a PrPSc monomer lie flat on a surface whereas in the 4R{beta}S model they wind in a corkscrew fashion. Here, we analyzed fully infectious recombinant PrPSc using a solid state NMR technique, PITHIRDS, that allows probing distances between specific labelled amino acid residues. To our surprise (as we have defended the 4R{beta}S model in the past), results clearly show the presence of a PIRIBS structure in our sample.

biochemistry↗

bioRxiv2020

Structural features of an infectious recombinant PrPSc prion using solid state NMR

PrPSc, the first described and most notorious prion, is the only protein known to cause epidemics of deadly disease. Its properties are encoded in its unique structure. Here we report a first solid state NMR study of a uniformly labelled (U-13C,15N)-Bank vole (BV) infectious recombinant PrPSc prion. C-C, C-H and N-H spectra were obtained with MAS rotation of the sample at up to 60 kHz. We obtained amino acid-type secondary structure information and used it to challenge a physically plausible atomistic model of PrPSc consisting of a 4-rung {beta} solenoid recently proposed by us. In all cases, our model was compatible with the data. This study shows that elucidation of the structure of PrPSc is within reach using recombinant PrPSc, NMR, and our model as a guiding tool.

biochemistry↗