Zinc-binding structure of a catalytic amyloid from solid-state NMR

Abstract

Throughout biology, amyloids are key structures in both functional proteins and the end product of pathologic protein misfolding. Amyloids might also represent an early precursor in the evolution of life because of their small molecular size and their ability to self-purify and catalyze chemical reactions. They also provide attractive backbones for advanced materials. When β-strands of an amyloid are arranged parallel and in register, side chains from the same position of each chain align, facilitating metal chelation when the residues are good ligands such as histidine. High-resolution structures of metalloamyloids are needed to understand the molecular bases of metal-amyloid interactions. Here we combine solid-state NMR and structural bioinformatics to determine the structure of a zinc-bound metalloamyloid that catalyzes ester hydrolysis. The peptide forms amphiphilic parallel β-sheets that assemble into stacked bilayers with alternating hydrophobic and polar interfaces. The hydrophobic interface is stabilized by apolar side chains from adjacent sheets, whereas the hydrated polar interface houses the Zn-binding histidines with binding geometries unusual in proteins. Each Zn has two bis-coordinated histidine ligands, which bridge adjacent strands to form an infinite metal-ligand chain along the fibril axis. A third histidine completes the protein ligand environment, leaving a free site on the Zn for water activation. This structure defines a class of materials, which we call metal-peptide frameworks. The structure reveals a delicate interplay through which metal ions stabilize the amyloid structure, which in turn shapes the ligand geometry and catalytic reactivity of Zn.

Enhanced Fluorescence for Bioassembly by Environment‐Switching Doping of Metal Ions

“…Likewise, BFPms1 (a green fluorescent protein mutant) and its derived aromatic short peptide tryptophan‐phenylalanine (linear‐WF) show high binding affinity to Zn(II) and assemble into supramolecular structures with enhanced fluorescence emission. However, although extensive efforts have been made in order to clarify the coordination mechanisms between metal ions and peptide assemblies, the very initial interactions between the metal ions and the peptide molecules, which guide their association into oligomeric clusters and subsequently into larger supramolecular structures underlying the molecular mechanism of photoactive features, are still elusive.…”

Exploiting Heterogeneous Time Scale of Dynamics to Enhance 2D HETCOR Solid-State NMR Sensitivity

“…After the initial CP period, the transverse 13 and then the magnetization is stored along the z axis by the following 90 o pulse for both mobile and rigid components. The HORROR sequence [60] is applied to remove any residual 1 H magnetization before 13 Cà 1 H CP. The 13 C magnetization from the rigid components is transferred to 1 H by the second CP for the first signal acquisition during t2 (to obtain the 2D Rigid-HETCOR spectrum).…”

“…(Mobile-HETCOR). During signal acquisitions of rigid and mobile components 13 C nuclei can be decoupled as indicted in the pulse sequence.…”

“…But, for a multiphase system constituting molecular components that differ in their time scales of mobilities, CP efficiency is pretty low for mobile components because of the averaging of heteronuclear dipolar couplings whereas INEPT is inefficient due to the short T2 of immobile components and can be non-selective due to strong proton spin diffusion for immobile components especially under moderate spinning speeds. Herein, in this study we present two 2D pulse sequences that enable the sequential acquisition of 13 C/ 1 H HETCOR NMR spectra for the rigid and mobile components by taking full advantage of the abundant proton magnetization in a single experiment with barely increasing the overall experimental time. In particular, the 13 C-detected HETCOR experiment could be applied under slow MAS conditions, where a multiple-pulse sequence is typically employed to enhance 1…”

“…Solid-state NMR spectroscopy is a powerful analytical tool that is widely used for studying molecular structures and dynamics of a variety of solids including membrane proteins, [1][2][3][4][5] multiphase polymers [6][7][8], bone materials, [9][10][11] amyloids [12][13][14][15][16][17], and nanocomposites [18][19][20][21]. The benefits of multidimensional NMR techniques to obtain higher resolution and higher degree of structural and dynamic information have been well utilized in numerous applications, among which 2D homonuclear (HOMCOR) [22][23][24][25] and heteronuclear (HETCOR) [26][27][28][29][30][31] chemical shift correlation experiments are most widely employed and have become indispensable for structural studies of proteins.…”