Annette Diehl

Structure of a protein determined by solid-state magic-angle-spinning NMR spectroscopy

The determination of a representative set of protein structures is a chief aim in structural genomics. Solid-state NMR may have a crucial role in structural investigations of those proteins that do not easily form crystals or are not accessible to solution NMR, such as amyloid systems or membrane proteins. Here we present a protein structure determined by solid-state magic-angle-spinning (MAS) NMR. Almost complete 13C and 15N resonance assignments for a micro-crystalline preparation of the α-spectrin Src-homology 3 (SH3) domain formed the basis for the extraction of a set of distance restraints. These restraints were derived from proton-driven spin diffusion (PDSD) spectra of biosynthetically site-directed, labelled samples obtained from bacteria grown using [1,3-13C]glycerol or [2-13C]glycerol as carbon sources. This allowed the observation of long-range distance correlations up to ∼7 Å. The calculated global fold of the α-spectrin SH3 domain is based on 286 inter-residue 13C–13C and six 15N–15N restraints, all self-consistently obtained by solid-state MAS NMR. This MAS NMR procedure should be widely applicable to small membrane proteins that can be expressed in bacteria.

Structural changes of TasA in biofilm formation of Bacillus subtilis

Significance Understanding the formation and structure of protective bacterial biofilms will help to design and identify antimicrobial strategies. Our experiments with the secreted major biofilm protein TasA characterize on a molecular level in vivo the transition of a folded protein into protease-resistant biofilm-stabilizing fibrils. Such conformational changes from a globular state into fibrillar structures are so far not seen for other biofilm-forming proteins. In this context, TasA can serve as a model system to study functional fibril formation from a globular state. Microorganisms form surface-attached communities, termed biofilms, which can serve as protection against host immune reactions or antibiotics. Bacillus subtilis biofilms contain TasA as major proteinaceous component in addition to exopolysaccharides. In stark contrast to the initially unfolded biofilm proteins of other bacteria, TasA is a soluble, stably folded monomer, whose structure we have determined by X-ray crystallography. Subsequently, we characterized in vitro different oligomeric forms of TasA by NMR, EM, X-ray diffraction, and analytical ultracentrifugation (AUC) experiments. However, by magic-angle spinning (MAS) NMR on live biofilms, a swift structural change toward only one of these forms, consisting of homogeneous and protease-resistant, β-sheet–rich fibrils, was observed in vivo. Thereby, we characterize a structural change from a globular state to a fibrillar form in a functional prokaryotic system on the molecular level.

The solution structure of the SODD BAG domain reveals additional electrostatic interactions in the HSP70 complexes of SODD subfamily BAG domains

The solution structure of an N‐terminally extended construct of the SODD BAG domain was determined by nuclear magnetic resonance spectroscopy. A homology model of the SODD‐BAG/HSP70 complex reveals additional possible interactions that are specific for the SODD subfamily of BAG domains while the overall geometry of the complex remains the same. Relaxation rate measurements show that amino acids N358–S375 of SODD which were previously assigned to its BAG domain are not structured in our construct. The SODD BAG domain is thus indeed smaller than the homologous domain in Bag1 defining a new subfamily of BAG domains.

The Structure of MESD45–184 Brings Light into the Mechanism of LDLR Family Folding

Mesoderm development (MESD) is a 224 amino acid mouse protein that acts as a molecular chaperone for the low-density lipoprotein receptor (LDLR) family. Here, we provide evidence that the region 45-184 of MESD is essential and sufficient for this function and suggest a model for its mode of action. NMR studies reveal a β-α-β-β-α-β core domain with an α-helical N-terminal extension that interacts with the β sheet in a dynamic manner. As a result, the structural ensemble contains open (active) and closed (inactive) forms, allowing for regulation of chaperone activity through substrate binding. The mutant W61R, which is lethal in Drosophila, adopts only the open state. The receptor motif recognized by MESD was identified by in vitro-binding studies. Furthermore, in vivo functional evidence for the relevance of the identified contact sites in MESD is provided.

The solution structure of the core of mesoderm development (MESD), a chaperone for members of the LDLR-family

Mesoderm development (MESD) is a 224 amino acid mouse protein that acts as a molecular chaperone for receptors of the low-density lipoprotein receptor (LDLR) family. By recording 15N-HSQC-NMR spectra of six different MESD constructs, we could determine a highly structured core region corresponding to residues 104-177. Here we firstly present the solution structure of this highly conserved core of MESD. It shows a four-stranded anti-parallel β-sheet and two α-helices situated on one side of the sheet. Although described in the literature as structurally homologues to ferredoxins, the connectivity of secondary structure elements is different in the MESD fold. A structural comparison to entries of the PDB reveals a frequent domain with low sequence homology annotated as HMA and P-II domains in Pfam.

Structural and biochemical characterization of Rv2140c, a phosphatidylethanolamine-binding protein from Mycobacterium tuberculosis

Rv2140c is one of many conserved Mycobacterium tuberculosis proteins for which no molecular function has been identified. We have determined a high‐resolution crystal structure of the Rv2140c gene product, which reveals a dimeric complex that shares strong structural homology with the phosphatidylethanolamine‐binding family of proteins. Rv2140c forms low‐millimolar interactions with a selection of soluble phosphatidylethanolamine analogs, indicating that it has a role in lipid metabolism. Furthermore, the small molecule locostatin binds to the Rv2140c ligand‐binding site and also inhibits the growth of the model organism Mycobacterium smegmatis.

Backbone and sidechain 1H, 13C and 15N resonance assignments of the RGS domain from human RGS14

We have assigned 1H, 15N and 13C resonances of the RGS domain from the human RGS14 protein, a multi-domain member of the RGS (Regulators of G-protein signalling) family of proteins, important in the down-regulation of specific G-protein signalling pathways.