Crystal structure of a small heat-shock protein from Xylella fastidiosa reveals a distinct high-order structure

What Can De Novo Protein Design Bring to the Treatment of Hematological Disorders?

Protein therapeutics have been widely used to treat hematological disorders. With the advent of de novo protein design, protein therapeutics are not limited to ameliorating natural proteins but also produce novel protein sequences, folds, and functions with shapes and functions customized to bind to the therapeutic targets. De novo protein techniques have been widely used biomedically to design novel diagnostic and therapeutic drugs, novel vaccines, and novel biological materials. In addition, de novo protein design has provided new options for treating hematological disorders. Scientists have designed protein switches called Colocalization-dependent Latching Orthogonal Cage-Key pRoteins (Co-LOCKR) that perform computations on the surface of cells. De novo designed molecules exhibit a better capacity than the currently available tyrosine kinase inhibitors in chronic myeloid leukemia therapy. De novo designed protein neoleukin-2/15 enhances chimeric antigen receptor T-cell activity. This new technique has great biomedical potential, especially in exploring new treatment methods for hematological disorders. This review discusses the development of de novo protein design and its biological applications, with emphasis on the treatment of hematological disorders.

Network of Entamoeba histolytica HSP18.5 dimers formed by two overlapping [IV]-X-[IV] motifs

Small heat shock proteins (sHSPs) are ATP-independent molecular chaperones with low molecular weight that prevent the aggregation of proteins during stress conditions and maintain protein homeostasis in the cell. sHSPs exist in dynamic equilibrium as a mixture of oligomers of various sizes with a constant exchange of subunits between them. Many sHSPs form cage-like assemblies that may dissociate into smaller oligomers during stress conditions. We carried out the functional and structural characterization of a small heat shock protein, HSP18.5, from Entamoeba histolytica (EhHSP18.5). It showed a pH-dependent change in its oligomeric state, which varied from a tetramer to larger than 48-mer. EhHSP18.5 protected Nde I and lysozyme substrates from temperature and chemical stresses, respectively. The crystal structure of EhHSP18.5 was determined at a resolution of 3.28 Å in C2221 cell with four subunits in the asymmetric unit forming two non-metazoan sHSP-type dimers. Unlike the reported cage-like structures, EhHSP18.5 formed a network of linear chains of molecules in the crystal. Instead of a single [IV]-X-[IV] motif, EhHSP18.5 has two overlapping I/V-X-I/V sequences at the C-terminus giving rise to novel interactions between the dimers. Negative staining Electron Microscopy images of EhHSP18.5 showed the presence of multiple oligomers: closed structures of various sizes and long tube-like structures.

Genome-wide screens identify Toxoplasma gondii determinants of parasite fitness in IFNγ-activated murine macrophages

Macrophages play an essential role in the early immune response against Toxoplasma and are the cell type preferentially infected by the parasite in vivo. Interferon gamma (IFNγ) elicits a variety of anti-Toxoplasma activities in macrophages. Using a genome-wide CRISPR screen we identify 353 Toxoplasma genes that determine parasite fitness in naїve or IFNγ-activated murine macrophages, seven of which are further confirmed. We show that one of these genes encodes dense granule protein GRA45, which has a chaperone-like domain, is critical for correct localization of GRAs into the PVM and secretion of GRA effectors into the host cytoplasm. Parasites lacking GRA45 are more susceptible to IFNγ-mediated growth inhibition and have reduced virulence in mice. Together, we identify and characterize an important chaperone-like GRA in Toxoplasma and provide a resource for the community to further explore the function of Toxoplasma genes that determine fitness in IFNγ-activated macrophages.

Transcriptome analysis reveals the effect of short-term sunlight on aroma metabolism in postharvest leaves of oolong tea(Camellia sinensis)

Tea (Camellia sinensis (L.)) is an important economic plant. Light is the earliest external signal factor during the postharvest processing of oolong tea, and the solar withering is an indispensable process for aroma formation. In this study, Tieguanyin was used to analyze the effect of sunlight on aroma metabolism, which indicated that the main aroma compounds were significantly increased during solar withering for 15 min compared to the indoor withering. In addition, differentially expressed genes related to aroma metabolism were identified and quantified using the high-throughput Illumina RNA-Seq technology. The expression levels of key regulatory genes were consistent with the results from the gas chromatography-time of flight mass spectrometry (GC-TOF-MS) analysis, especially in terpenoid metabolic pathway, which showed that aroma metabolism could significantly respond to the short-term light, while its expression level was easily inhibited by the up-regulation of heat shock protein. Taken together, those data provides further insights into the mechanisms, contributing to aroma metabolism of tea plant.

Biophysical and structural characterization of the small heat shock protein HspA from Thermosynechococcus vulcanus in 2 M urea

Small heat shock proteins (sHSPs) belong to the superfamily of molecular chaperones. They prevent aggregation of partially unfolded or misfolded client proteins, providing protection to organisms under stress conditions. Here, we report the biophysical and structural characterization of a small heat shock protein (HspA) from a thermophilic cyanobacterium Thermosynechococcus vulcanus in the presence of 2 M urea. HspA has been shown to be important for the protection of Photosystem II and the Phycobilisome antenna complex at elevated temperatures. Heterologously expressed HspA requires the presence of 1-2 M urea to maintain its solubility at concentrations required for most characterization methods. Spectroscopic studies reveal the presence of the β-sheet structure and intactness of the tertiary fold in HspA. In vitro assays show that the HspA maintains chaperone-like activity in protecting soluble proteins from thermal aggregation. Chromatography and electron microscopy show that the HspA exists as a mixture of oligomeric forms in the presence of 2 M urea. HspA was successfully crystallized only in the presence of 2 M urea. The crystal structure of HspA shows urea-induced loss of about 30% of the secondary structure without major alteration in the tertiary structure of the protein. The electron density maps reveal changes in the hydrogen bonding network which we attribute to the presence of urea. The crystal structure of HspA demonstrates a mixture of both direct interactions between urea and protein functionalities and interactions between urea and the surrounding solvent that indirectly affect the protein, which are in accordance with previously published studies.