Solid state NMR chemical shift assignment and conformational analysis of a cellulose binding protein facilitated by optimized glycerol enrichment

Nonuniformly sampled exclusively-13 C/15 N 4D solid-state NMR experiments: Assignment and characterization of IKe phage capsid

An important step in the process of protein research by NMR is the assignment of chemical shifts. In the coat protein of IKe bacteriophage, there are 53 residues making up a long helix resulting in relatively high spectral ambiguity. Assignment thus requires the collection of a set of three-dimensional (3D) experiments and the preparation of sparsely labeled samples. Increasing the dimensionality can facilitate fast and reliable assignment of IKe and of larger proteins. Recent progress in nonuniform sampling techniques made the application of multidimensional NMR solid-state experiments beyond 3D more practical. 4D ¹ H-detected experiments have been demonstrated in high-fields and at spinning speeds of 60 kHz and higher but are not practical at spinning speeds of 10-20 kHz for fully protonated proteins. Here, we demonstrate the applicability of a nonuniformly sampled 4D ¹³ C/¹⁵ N-only correlation experiment performed at a moderate field of 14.1 T, which can incorporate sufficiently long acquisition periods in all dimensions. We show how a single CANCOCX experiment, supported by several 2D carbon-based correlation experiments, is utilized for the assignment of heteronuclei in the coat protein of the IKe bacteriophage. One sparsely labeled sample was used to validate sidechain assignment of several hydrophobic-residue sidechains. A comparison to solution NMR studies of isolated IKe coat proteins embedded in micelles points to key residues involved in structural rearrangement of the capsid upon assembly of the virus. The benefits of 4D to a quicker assignment are discussed, and the method may prove useful for studying proteins at relatively low fields.

Structure and Dynamics of Polysaccharides in Plant Cell Walls from Solid-State NMR

Multidimensional high-resolution magic-angle-spinning solid-state NMR (SSNMR) spectroscopy has recently been shown to have the unique capability of revealing the molecular structure and dynamics of insoluble macromolecules in intact plant cell walls. This chapter summarizes the 2D and 3D SSNMR techniques used so far to study cell walls and key findings about cellulose interactions with matrix polysaccharides, cellulose microfibril structure, polysaccharide–protein interactions that are responsible for wall loosening, and polysaccharide–water interactions in the hydrated primary walls. These results provide detailed molecular insights into the structure of near-native plant cell walls, and revise the conventional tethered-network model by suggesting a single-network model for the primary cell wall, which has found increasing support from recent biochemical and biomechanical data.

Magic angle spinning NMR of viruses

Viruses, relatively simple pathogens, are able to replicate in many living organisms and to adapt to various environments. Conventional atomic-resolution structural biology techniques, X-ray crystallography and solution NMR spectroscopy provided abundant information on the structures of individual proteins and nucleic acids comprising viruses; however, viral assemblies are not amenable to analysis by these techniques because of their large size, insolubility, and inherent lack of long-range order. In this article, we review the recent advances in magic angle spinning NMR spectroscopy that enabled atomic-resolution analysis of structure and dynamics of large viral systems and give examples of several exciting case studies.