Structure-guided design of VAR2CSA-based immunogens and a cocktail strategy for a placental malaria vaccine.

Placental accumulation of Plasmodium falciparum infected erythrocytes results in maternal anemia, low birth weight, and pregnancy loss. The parasite protein VAR2CSA facilitates the accumulation of infected erythrocytes in the placenta through interaction with the host receptor chondroitin sulfate A (CSA). Antibodies that prevent the VAR2CSA-CSA interaction correlate with protection from placental malaria, and VAR2CSA is a high-priority placental malaria vaccine antigen.

Structural and functional comparisons of salivary α-glucosidases from the mosquito vectors Aedes aegypti, Anopheles gambiae, and Culex quinquefasciatus.

Mosquito vectors of medical importance both blood and sugar feed, and their saliva contains bioactive molecules that aid in both processes. Although it has been shown that the salivary glands of several mosquito species exhibit α-glucosidase activities, the specific enzymes responsible for sugar digestion remain understudied. We therefore expressed and purified three recombinant salivary α-glucosidases from the mosquito vectors Aedes aegypti, Anopheles gambiae, and Culex quinquefasciatus and compared their functions and structures.

Structural and immunological differences in Plasmodium falciparum sexual stage transmission-blocking vaccines comprised of Pfs25-EPA nanoparticles.

Development of a malaria vaccine that blocks transmission of different parasite stages to humans and mosquitoes is considered critical for elimination efforts. A vaccine using Pfs25, a protein on the surface of zygotes and ookinetes, is under investigation as a transmission-blocking vaccine (TBV) that would interrupt parasite passage from mosquitoes to humans. The most extensively studied Pfs25 TBVs use Pichia pastoris-produced recombinant forms of Pfs25, chemically conjugated to a recombinant carrier protein, ExoProtein A (EPA).

Functional aspects of evolution in a cluster of salivary protein genes from mosquitoes.

The D7 proteins are highly expressed in the saliva of hematophagous Nematocera and bind biogenic amines and eicosanoid compounds produced by the host during blood feeding. These proteins are encoded by gene clusters expressing forms having one or two odorant-binding protein-like domains. Here we examine functional diversity within the D7 group in the genus Anopheles and make structural comparisons with D7 proteins from culicine mosquitoes in order to understand aspects of D7 functional evolution.

Piwi4 Structural Features Are Necessary for RNA Binding and Nuclear Localization.

The PIWI-interacting RNA (piRNA) pathway provides an RNA interference (RNAi) mechanism known from studies to maintain the integrity of the germline genome by silencing transposable elements (TE). mosquitoes, which are the key vectors of several arthropod-borne viruses, exhibit an expanded repertoire of Piwi proteins involved in the piRNA pathway, suggesting functional divergence. Here, we investigate RNA-binding dynamics and subcellular localization of Piwi4 (AePiwi4), a Piwi protein involved in antiviral immunity and embryonic development, to better understand its function.

The structures of two salivary proteins from the West Nile vector reveal a beta-trefoil fold with putative sugar binding properties.

Female mosquitoes require blood meals for egg development. The saliva of blood feeding arthropods contains biochemically active molecules, whose anti-hemostatic and anti-inflammatory properties facilitate blood feeding on vertebrate hosts. While transcriptomics has presented new opportunities to investigate the diversity of salivary proteins from hematophagous arthropods, many of these proteins remain functionally undescribed.

Structure and function of a malaria transmission blocking vaccine targeting Pfs230 and Pfs230-Pfs48/45 proteins.

Proteins Pfs230 and Pfs48/45 are Plasmodium falciparum transmission-blocking (TB) vaccine candidates that form a membrane-bound protein complex on gametes. The biological role of Pfs230 or the Pfs230-Pfs48/45 complex remains poorly understood. Here, we present the crystal structure of recombinant Pfs230 domain 1 (Pfs230D1M), a 6-cysteine domain, in complex with the Fab fragment of a TB monoclonal antibody (mAb) 4F12.

ADP binding by the Culex quinquefasciatus mosquito D7 salivary protein enhances blood feeding on mammals.

During blood-feeding, mosquito saliva is injected into the skin to facilitate blood meal acquisition. D7 proteins are among the most abundant components of the mosquito saliva. Here we report the ligand binding specificity and physiological relevance of two D7 long proteins from Culex quinquefasciatus mosquito, the vector of filaria parasites or West Nile viruses.

The 2.1 Å structure of protein F9 and its comparison to L1, two components of the conserved poxvirus entry-fusion complex.

The poxvirus F9 protein is a component of the vaccinia virus entry fusion complex (EFC) which consists of 11 proteins. The EFC forms a unique apparatus among viral fusion proteins and complexes. We solved the atomic structure of the F9 ectodomain at 2.

Kinetics and Thermodynamics of DbpA Protein's C-Terminal Domain Interaction with RNA.

DbpA is an DEAD-box RNA helicase implicated in RNA structural isomerization in the peptide bond formation site. In addition to the RecA-like catalytic core conserved in all of the members of DEAD-box family, DbpA contains a structured C-terminal domain, which is responsible for anchoring DbpA to hairpin 92 of 23S ribosomal RNA during the ribosome assembly process. Here, surface plasmon resonance was used to determine the equilibrium dissociation constant and the microscopic rate constants of the DbpA C-terminal domain association and dissociation to a fragment of 23S ribosomal RNA containing hairpin 92.

Biochemical and biophysical characterization of cytokine-like protein 1 (CYTL1).

Cytokine-like protein 1 (CYTL1) is a small widely expressed secreted protein lacking significant primary sequence homology to any other known protein. CYTL1 expression appears to be highest in the hematopoietic system and in chondrocytes; however, maintenance of cartilage in mouse models of arthritis is its only reported function in vivo. Despite lacking sequence homology to chemokines, CYTL1 is predicted by computational methods to fold like a chemokine, and has been reported to function as a chemotactic agonist at the chemokine receptor CCR2 in mouse monocyte/macrophages.

The Vaccinia Virus H3 Envelope Protein, a Major Target of Neutralizing Antibodies, Exhibits a Glycosyltransferase Fold and Binds UDP-Glucose.

Unlabelled: The highly conserved H3 poxvirus protein is a major target of the human antibody response against poxviruses and is likely a key contributor to protection against infection. Here, we present the crystal structure of H3 from vaccinia virus at a 1.9-Å resolution.

Hfqs in Bacillus anthracis: Role of protein sequence variation in the structure and function of proteins in the Hfq family.

Hfq proteins in Gram-negative bacteria play important roles in bacterial physiology and virulence, mediated by binding of the Hfq hexamer to small RNAs and/or mRNAs to post-transcriptionally regulate gene expression. However, the physiological role of Hfqs in Gram-positive bacteria is less clear. Bacillus anthracis, the causative agent of anthrax, uniquely expresses three distinct Hfq proteins, two from the chromosome (Hfq1, Hfq2) and one from its pXO1 virulence plasmid (Hfq3).

Molecular insights into the binding of coenzyme F420 to the conserved protein Rv1155 from Mycobacterium tuberculosis.

Coenzyme F420 is a deazaflavin hydride carrier with a lower reduction potential than most flavins. In Mycobacterium tuberculosis (Mtb), F420 plays an important role in activating PA-824, an antituberculosis drug currently used in clinical trials. Although F420 is important to Mtb redox metabolism, little is known about the enzymes that bind F420 and the reactions that they catalyze.

The structure of the poxvirus A33 protein reveals a dimer of unique C-type lectin-like domains.

The current vaccine against smallpox is an infectious form of vaccinia virus that has significant side effects. Alternative vaccine approaches using recombinant viral proteins are being developed. A target of subunit vaccine strategies is the poxvirus protein A33, a conserved protein in the Chordopoxvirinae subfamily of Poxviridae that is expressed on the outer viral envelope.

Structure of the DBL3x domain of pregnancy-associated malaria protein VAR2CSA complexed with chondroitin sulfate A.

Plasmodium falciparum-infected erythrocytes bind to chondroitin sulfate A (CSA) in the placenta via the VAR2CSA protein, a member of the P. falciparum erythrocyte membrane protein-1 family, leading to life-threatening malaria in pregnant women with severe effects on their fetuses and newborns. Here we describe the structure of the CSA binding DBL3x domain, a Duffy binding-like (DBL) domain of VAR2CSA.

The cysteine-rich interdomain region from the highly variable plasmodium falciparum erythrocyte membrane protein-1 exhibits a conserved structure.

Plasmodium falciparum malaria parasites, living in red blood cells, express proteins of the erythrocyte membrane protein-1 (PfEMP1) family on the red blood cell surface. The binding of PfEMP1 molecules to human cell surface receptors mediates the adherence of infected red blood cells to human tissues. The sequences of the 60 PfEMP1 genes in each parasite genome vary greatly from parasite to parasite, yet the variant PfEMP1 proteins maintain receptor binding.

Structural basis for the binding of the neutralizing antibody, 7D11, to the poxvirus L1 protein.

Medical countermeasures to prevent or treat smallpox are needed due to the potential use of poxviruses as biological weapons. Safety concerns with the currently available smallpox vaccine indicate a need for research on alternative poxvirus vaccine strategies. Molecular vaccines involving the use of proteins and/or genes and recombinant antibodies are among the strategies under current investigation.

High apparent dielectric constant inside a protein reflects structural reorganization coupled to the ionization of an internal Asp.

The dielectric properties of proteins are poorly understood and difficult to describe quantitatively. This limits the accuracy of methods for structure-based calculation of electrostatic energies and pK(a) values. The pK(a) values of many internal groups report apparent protein dielectric constants of 10 or higher.

Influence of ions, hydration, and the transcriptional inhibitor P4N on the conformations of the Sp1 binding site.

Three crystal structures containing the entire Sp1 consensus sequence d(GGGGCGGGG) with two or three additional base-pairs on either the 5' or 3' ends and overhangs have been determined. Despite the different lengths of DNA in the pseudo-dodecamers and pseudo-tridecamer, all three structures form A-DNA duplexes that share a common set of crystal contacts, including a T*(G.C) base triplet and a 5'-overhang that flips out and away from the helical axes to form a Hoogsteen base-pair with the 3'-overhang of a symmetry mate.

X-ray and thermodynamic studies of staphylococcal nuclease variants I92E and I92K: insights into polarity of the protein interior.

We have used crystallography and thermodynamic analysis to study nuclease variants I92E and I92K, in which an ionizable side-chain is placed in the hydrophobic core of nuclease. We find that the energetic cost of burying ionizable groups is rather modest. The X-ray determinations show water molecules solvating the buried glutamic acid under cryo conditions, but not at room temperature.

A compact RNA tertiary structure contains a buried backbone-K+ complex.

The structure of a 58 nucleotide ribosomal RNA fragment buries several phosphate groups of a hairpin loop within a large tertiary core. During refinement of an X-ray crystal structure containing this RNA, a potassium ion was found to be contacted by six oxygen atoms from the buried phosphate groups; the ion is contained completely within the solvent-accessible surface of the RNA. The electrostatic potential at the ion chelation site is unusually large, and more than compensates for the substantial energetic penalties associated with partial dehydration of the ion and displacement of delocalized ions.