Pheromone peptide cOB1 from native Enterococcus faecalis forms amyloid-like structures: A new paradigm for peptide pheromones

Pheromone peptides are an important component of bacterial quorum-sensing system. The pheromone peptide cOB1 (VAVLVLGA) of native commensal Enterococcus faecalis has also been identified as an antimicrobial peptide (AMP) and reported to kill the prototype clinical isolate strain of E. faecalis V583. In this study, the pheromone peptide cOB1 has shown to form amyloid-like structures, a characteristic which is never reported for a pheromone peptide so far. With in silico analysis, the peptide was predicted to be highly amyloidogenic. Further, under experimental conditions, cOB1 formed aggregates displaying characteristics of amyloid structures such as bathochromic shift in Congo red absorbance, enhancement in thioflavin T fluorescence, and fibrillar morphology under transmission electron microscopy. This novel property of pheromone peptide cOB1 may have some direct effects on the binding of the pheromone to the receptor cells and subsequent conjugative transfer, making this observation more important for the therapeutics, dealing with the generation of virulent and multidrug-resistant pathogenic strains.

Design, Synthesis and Biological Evaluation of 1-Phenyl-2-(phenylamino) Ethanone Derivatives as Novel MCR-1 Inhibitors

Polymyxins are considered to be the last-line antibiotics that are used to treat infections caused by multidrug-resistant (MDR) gram-negative bacteria; however, the plasmid-mediated transferable colistin resistance gene (mcr-1) has rendered polymyxins ineffective. Therefore, the protein encoded by mcr-1, MCR-1, could be a target for structure-based design of inhibitors to tackle polymyxins resistance. Here, we identified racemic compound 3 as a potential MCR-1 inhibitor by virtual screening, and 26 compound 3 derivatives were synthesized and evaluated in vitro. In the cell-based assay, compound 6g, 6h, 6i, 6n, 6p, 6q, and 6r displayed more potent activity than compound 3. Notably, 25 μΜ of compound 6p or 6q combined with 2 μg·mL-1 colistin could completely inhibit the growth of BL21(DE3) expressing mcr-1, which exhibited the most potent activity. In the enzymatic assay, we elucidate that 6p and 6q could target the MCR-1 to inhibit the activity of the protein. Additionally, a molecular docking study showed that 6p and 6q could interact with Glu246 and Thr285 via hydrogen bonds and occupy well the cavity of the MCR-1 protein. These results may provide a potential avenue to overcome colistin resistance, and provide some valuable information for further investigation on MCR-1 inhibitors.

Ultra-Small Pd(0) Nanoparticles into a Designed Semisynthetic Lipase: An Efficient and Recyclable Heterogeneous Biohybrid Catalyst for the Heck Reaction under Mild Conditions

A novel heterogeneous enzyme-palladium (Pd) (0) nanoparticles (PdNPs) bionanohybrid has been synthesized by an efficient, green, and straightforward methodology. A designed Geobacillus thermocatenulatus lipase (GTL) variant genetically and then chemically modified by the introduction of a tailor-made cysteine-containing complementary peptide- was used as the stabilizing and reducing agent for the in situ formation of ultra-small PdNPs nanoparticles embedded on the protein structure. This bionanohybrid was an excellent catalyst in the synthesis of trans-ethyl cinnamate by Heck reaction at 65 °C. It showed the best catalytic performance in dimethylformamide (DMF) containing 10–25% of water as a solvent but was also able to catalyze the reaction in pure DMF or with a higher amount of water as co-solvent. The recyclability and stability were excellent, maintaining more than 90% of catalytic activity after five cycles of use.

Co-Evolutionary Fitness Landscapes for Sequence Design

Efficient and accurate models to predict the fitness of a sequence would be extremely valuable in protein design. We have explored the use of statistical potentials for the coevolutionary fitness landscape, extracted from known protein sequences, in conjunction with Monte Carlo simulations, as a tool for design. As proof of principle, we created a series of predicted high-fitness sequences for three different protein folds, representative of different structural classes: the GA (all-α) and GB (α/β) binding domains of streptococcal protein G, and an SH3 (all-β) domain. We found that most of the designed proteins can fold stably to the target structure, and a structure for a representative of each for GA, GB and SH3 was determined. Several of our designed proteins were also able to bind to native ligands, in some cases with higher affinity than wild-type. Thus, a search using a statistical fitness landscape is a remarkably effective tool for finding novel stable protein sequences.

Synthesis of a Stable Analog of the Phosphorylated Form of CheY: Phosphono-CheY

CheY is a response regulator of bacterial chemotaxis that is activated by phosphorylation of a conserved aspartate residue. However, studies of CheY-phosphate have proven challenging due to rapid hydrolysis of the aspartyl-phosphate in vitro. To combat this issue, we have designed a stable analog suitable for structural and functional studies. Herein, we describe a method for the chemical modification of Thermotoga maritima CheY to produce a phospho-analog designated as phosphono-CheY. Our modification produces a stable analog in the constitutively active form that enables the study of signal transfer to the downstream target.

Bioengineering Bacterially Derived Immunomodulants: A Therapeutic Approach to Inflammatory Bowel Disease

Bacterial enteric pathogens have evolved efficient mechanisms to suppress mammalian inflammatory and immunoregulatory pathways. By exploiting the evolutionary relationship between the gut and pathogenic bacteria, we have developed a potential mucosal therapeutic. Our findings suggest that engineered preparations of the Salmonella acetyltransferase, AvrA, suppress acute inflammatory responses such as those observed in inflammatory bowel disease (IBD). We created 125 nm diameter cross-linked protein nanoparticles directly from AvrA and carrier protein to deliver AvrA in the absence of Salmonella. AvrA nanoparticles are internalized in vitro and in vivo into barrier epithelial and lamina propria monocytic cells. AvrA nanoparticles inhibit inflammatory signaling and confer cytoprotection in vitro, and in murine colitis models, we observe decreased clinical and histological indices of inflammation. Thus, we have combined naturally evolved immunomodulatory proteins with modern bioengineering to produce AvrA nanoparticles, a potential treatment for IBD.

Instantaneous ion configurations in the K+ ion channel selectivity filter revealed by 2D IR spectroscopy

Potassium channels are responsible for the selective permeation of K+ ions across cell membranes. K+ ions permeate in single file through the selectivity filter, a narrow pore lined by backbone carbonyls that compose four K+ binding sites. Here, we report on the two-dimensional infrared (2D IR) spectra of a semisynthetic KcsA channel with site-specific heavy (13C18O) isotope labels in the selectivity filter. The ultrafast time resolution of 2D IR spectroscopy provides an instantaneous snapshot of the multi-ion configurations and structural distributions that occur spontaneously in the filter. Two elongated features are resolved, revealing the statistical weighting of two structural conformations. The spectra are reproduced by molecular dynamics simulations of structures with water separating two K+ ions in the binding sites, ruling out configurations with ions occupying adjacent sites.

Towards Structural Determination of the ComX Pheromone: Synthetic Studies on Peptides Containing Geranyltryptophan

Bacteria produce and respond to signal molecules depending on their cell density. This process is called "quorum sensing". The ComX pheromone, controlled by quorum sensing, activates natural genetic competence in Bacillus subtilis. ComX is an oligopeptide with a posttranslational modification. It has been suggested that ComX pheromone is modified with an isoprenoid at its tryptophan residue, but the complete chemical structure is unknown. We first determined the molecular formula of ComX(RO-E-2), a competence factor for B. subtilis strain RO-E-2. Then we synthesized putative pheromones with 1-, 2-, 4-, 5-, 6-, or 7-geranyl substituted tryptophan residues. The regio- and stereo-selective synthesis of the geranyl tryptophans was successful, and we prepared the six peptides with modified tryptophan residues. These peptides had the same molecular formula and showed similar hydrophobicity to the natural ComX(RO-E-2) in LC-MS analysis. But, none of them showed the same retention time as the natural pheromone and none exhibited its biological activity. These results suggest that the isoprenoid modification pattern of the tryptophan residue is more complex than postulated.

Structural characterization by NMR of a double phosphorylated chimeric peptide vaccine for treatment of Alzheimer's disease

Rational design of peptide vaccines becomes important for the treatment of some diseases such as Alzheimer's disease (AD) and related disorders. In this study, as part of a larger effort to explore correlations of structure and activity, we attempt to characterize the doubly phosphorylated chimeric peptide vaccine targeting a hyperphosphorylated epitope of the Tau protein. The 28-mer linear chimeric peptide consists of the double phosphorylated B cell epitope Tau₂₂₉₋₂₃₇[pThr231/pSer235] and the immunomodulatory T cell epitope Ag85B₂₄₁₋₂₅₅ originating from the well-known antigen Ag85B of the Mycobacterium tuberculosis, linked by a four amino acid sequence -GPSL-. NMR chemical shift analysis of our construct demonstrated that the synthesized peptide is essentially unfolded with a tendency to form a β-turn due to the linker. In conclusion, the -GPSL- unit presumably connects the two parts of the vaccine without transferring any structural information from one part to the other. Therefore, the double phosphorylated epitope of the Tau peptide is flexible and accessible.

Visual automated macromolecular model building

Automated model-building software aims at the objective interpretation of crystallographic diffraction data by means of the construction or completion of macromolecular models. Automated methods have rapidly gained in popularity as they are easy to use and generate reproducible and consistent results. However, the process of model building has become increasingly hidden and the user is often left to decide on how to proceed further with little feedback on what has preceded the output of the built model. Here, ArpNavigator, a molecular viewer tightly integrated into the ARP/wARP automated model-building package, is presented that directly controls model building and displays the evolving output in real time in order to make the procedure transparent to the user.

Semisynthesis of K+ channels

The ability to selectively conduct K(+) ions is central to the function of K(+) channels. Selection for K(+) and rejection of Na(+) takes place in a conserved structural element referred to as the selectivity filter. The selectivity filter consists of four K(+)-specific ion binding sites that are created using predominantly the backbone carbonyl oxygen atoms. Due to the involvement of the protein backbone, experimental manipulation of the ion binding sites in the selectivity filter is not possible using traditional site directed mutagenesis. The limited suitability of the site-directed mutagenesis for studies on the selectivity filter has motivated the development of a semisynthesis approach, which enables the use of chemical synthesis to manipulate the selectivity filter. In this chapter, we describe the protocols that are presently used in our laboratory for the semisynthesis of the bacterial K(+) channel, KcsA. We show the introduction of a spectroscopic probe into the KcsA channel using semisynthesis. We also review previous applications of semisynthesis in investigations of K(+) channels. While the protocols described in this chapter are for the KcsA K(+) channel, we anticipate that similar protocols will also be applicable for the semisynthesis of other integral membrane proteins.

Evaluation of a novel therapeutic approach to treating severe pneumococcal infection using a mouse model

P4, a 28-amino-acid peptide, is a eukaryotic cellular activator that enhances specific in vitro opsonophagocytic killing of multiple bacterial pathogens. In a previous study, we successfully recreated this phenomenon in mice in vivo by using a two-dose regimen of P4 and pathogen-specific antibodies, which significantly reduced moribundity in mice. For the present study, we hypothesized that the inclusion of a low-dose antibiotic would make it possible to treat the infected mice with a single dose containing a mixture of P4 and a pathogen-specific antibody. A single dose consisting of P4, intravenous immunoglobulin (IVIG), and ceftriaxone effectively reduced moribundity compared to that of untreated controls (n = 10) by 75% (P < 0.05) and rescued all (10 of 10) infected animals (P < 0.05). If rescued animals were reinfected with Streptococcus pneumoniae and treated with a single dose containing P4, IVIG, and ceftriaxone, they could be rerescued. This observation of the repeated successful use of P4 combination therapy demonstrates a low risk of tolerance development. Additionally, we examined the polymorphonuclear leukocytes (PMN) derived from infected mice and observed that P4 enhanced in vitro opsonophagocytic killing (by >80% over the control level; P < 0.05). This finding supports our hypothesis that PMN are activated by P4 during opsonophagocytosis and the recovery of mice from pneumococcal infection. P4 peptide-based combination therapy may offer an alternative and rapid immunotherapy to treat fulminant pneumococcal infection.

A Facile Synthetic Method for Conversion of Chlorophyll-a to Bacteriochlorophyll-c

A simple synthetic route for converting chlorophyll(Chl)-a to bacteriochlorophyll(BChl)-c is described. Methyl bacteriopheophorbide(MBPhe)-d, easily obtained from Chl-a, was selectively brominated at the 20-position with pyridinium tribromide, and the following Suzuki-coupling with methylboronic acid afforded ca. a 4:1 mixture of desired MBPhe-c (20-Me) and debrominated MBPhe-d (20-H) in quantitative yield. Separation of MBPhe-c, transesterification of the 17-propionate group (Me --> farnesyl), and magnesium insertion successfully led to naturally occurring BChl-c.

Classification of proteins based on minimal modular repeats: lessons from nature in protein design

Proteins containing internal repeats within their primary sequence have received increased attention recently, as the extent of their presence in various organisms is recognized more fully, and their role in evolution is more thoroughly studied. Presented here is a technique used to detect and classify proteins based on a modular evolutionary phenomenon that results in a series of small internal repeats. The parameters chosen are based on a minimum segment of seven residues that result in simple functional scaffolds. The genomes and corresponding proteomes of a variety of eubacteria and archaea have been analyzed using an algorithm that searches prokaryotic genomes for proteins containing small conserved repeats assembled in a modular fashion similar to a recently characterized protein from the organism Nitrosomonas europaea. This analysis has revealed additional proteins present in N. europaea with similar modular characteristics. A further survey of a variety of organisms demonstrates that this evolutionary pathway has been utilized in other organisms as well, to yield a broad assortment of small modular proteins. A thorough description of the sequential characteristics of these modular proteins follows, along with a selection and discussion of the various proteins uncovered through this expanded search and analysis. Several databases of the proteins uncovered from this work and the program used to perform the search are available.

Structural and mechanistic exploration of acid resistance: kinetic stability facilitates evolution of extremophilic behavior

Kinetically stable proteins are unique in that their stability is determined solely by kinetic barriers rather than by thermodynamic equilibria. To better understand how kinetic stability promotes protein survival under extreme environmental conditions, we analyzed the unfolding behavior and determined the structure of Nocardiopsis alba Protease A (NAPase), an acid-resistant, kinetically stable protease, and compared these results with a neutrophilic homolog, alpha-lytic protease (alphaLP). Although NAPase and alphaLP have the same number of acid-titratable residues, kinetic studies revealed that the height of the unfolding free energy barrier for NAPase is less sensitive to acid than that of alphaLP, thereby accounting for NAPase's improved tolerance of low pH. A comparison of the alphaLP and NAPase structures identified multiple salt-bridges in the domain interface of alphaLP that were relocated to outer regions of NAPase, suggesting a novel mechanism of acid stability in which acid-sensitive electrostatic interactions are rearranged to similarly affect the energetics of both the native state and the unfolding transition state. An acid-stable variant of alphaLP in which a single interdomain salt-bridge is replaced with a corresponding intradomain NAPase salt-bridge shows a dramatic >15-fold increase in acid resistance, providing further evidence for this hypothesis. These observations also led to a general model of the unfolding transition state structure for alphaLP protease family members in which the two domains separate from each other while remaining relatively intact themselves. These results illustrate the remarkable utility of kinetic stability as an evolutionary tool for developing longevity over a broad range of harsh conditions.

The chemical synthesis of the GstI protein by NCL on a X-Met site

The small GstI protein (63 amino acids) of Rhizobium leguminosarum is the endogenous inhibitor of the glnII (glutamine synthetase II) gene expression. It has been suggested that GstI has a predominantly beta-structure and mediates the block of translation and stabilization of glnII mRNA through direct binding to its 5' untranslated region. Because of the unavailability of adequate amounts of purified recombinant protein, the mechanism as well as the protein tridimensional structure remain very poorly understood. To obtain the full-length protein, we have undertaken the chemical synthesis of the protein by different approaches. In a first attempt, the stepwise synthesis was unsuccessful, with strong aggregation experienced on the N-terminal side, after residue 44 from the C-terminus. In a second approach, we set up the conditions to carry out a native chemical ligation (NCL). Albeit the protein contains two Cysteine residues, located at positions 40 and 47, to minimize the size of the N-terminal segment to be synthesized, we have devised an alternative strategy of ligation on Met32, utilizing homoCys as the ligating moiety and then alkylating the resulting polypeptide with methyl iodide. New conditions to quantitatively methylate thiol groups in complex polypeptides have been conceived, obtaining the protein in very good yields and purity. A CD spectroscopy investigation has revealed that the protein does not adopt canonical secondary structures but is very rich in beta-structure (approximately 60%), in agreement with a previous study carried out on samples obtained by recombinant methods.

Synthesis and in vitro biocompatibility of injectable polyurethane foam scaffolds

The development of therapeutics for orthopedic clinical indications exploiting minimally invasive surgical techniques has substantial benefits, especially for treatment of fragility fractures in the distal radius of osteoporotics and vertebral compression fractures. We have designed six formulations of injectable polyurethane foams to address these clinical indications. The polyurethanes were prepared by mixing two liquid components and injecting the reactive liquid mixture into a mold where it hardens in situ. Porous polyurethane foams were synthesized from lysine methyl ester diisocyanate, a poly(epsilon-caprolactone-co-glycolide) triol, a tertiary amine catalyst, anionic and non-ionic stabilizers, and a fatty acid pore opener. The rise time of the foams varied from 8-20 min. The porosity was approximately 95% and the pores varied in size from 100-1000 microm. The polyurethane foams supported attachment of viable (>95%) MG-63 cells under dynamic seeding conditions. We anticipate compelling opportunities will be available as a consequence of the favorable biological and physical properties of the injectable polyurethane foams.

Synthesis of asparagine-linked bacillosamine

Various types of protein glycosylation have been identified from prokaryotes. Recent investigations have revealed the presence of N-linked glycoproteins in the pathogenic bacterium, Campylobacter jejuni. The structure of this glycan is unique, consisting of 5 GalNAc and 1 Glc, in addition to 2,4-diacetamido-2,4,6-trideoxy-d-glucopyranose (bacillosamine; Bac), which is N-glycosidically linked to the side chain of asparagine (Asn). We synthesized Bac from a 2-azido-2-deoxy-D-galactose derivative, which was further converted to the Asn-linked form.

Computational Design of a New Hydrogen Bond Network and at Least a 300-fold Specificity Switch at a Protein−Protein Interface

The redesign of protein-protein interactions is a stringent test of our understanding of molecular recognition and specificity. Previously we engineered a modest specificity switch into the colicin E7 DNase-Im7 immunity protein complex by identifying mutations that are disruptive in the native complex, but can be compensated by mutations on the interacting partner. Here we extend the approach by systematically sampling alternate rigid body orientations to optimize the interactions in a binding mode specific manner. Using this protocol we designed a de novo hydrogen bond network at the DNase-immunity protein interface and confirmed the design with X-ray crystallographic analysis. Subsequent design of the second shell of interactions guided by insights from the crystal structure on tightly bound water molecules, conformational strain, and packing defects yielded new binding partners that exhibited specificities of at least 300-fold between the cognate and the non-cognate complexes. This multi-step approach should be applicable to the design of polar protein-protein interactions and contribute to the re-engineering of regulatory networks mediated by protein-protein interactions.

Total chemical synthesis of the B1 domain of protein L from Peptostreptococcus magnus

Reported here is a native chemical ligation strategy for the total chemical synthesis of the B1 domain of protein L. A synthetic construct of this 76 amino acid protein domain was prepared by the chemoselective ligation of two unprotected polypeptide fragments, one containing an N-terminal cysteine residue and one containing a C-terminal thioester moiety. The polypeptide fragments utilized in the ligation reaction were readily prepared by stepwise solid phase peptide synthesis (SPPS) methods for Boc-chemistry. The milligram quantities of protein required for conventional biophysical studies were readily accessible using the synthetic protocol described here. The folding properties of the synthetic protein L construct were also determined and found to be very similar to those of a similar wild-type protein L constructs prepared by recombinant-DNA methods. This work facilitates future unnatural amino acid mutagenesis experiments on this model protein system to further dissect the molecular basis of its folding and stability.

A hydrophobic patch in the competence-stimulating Peptide, a pneumococcal competence pheromone, is essential for specificity and biological activity

Induction of competence for natural genetic transformation in Streptococcus pneumoniae depends on pheromone-mediated cell-cell communication and a signaling pathway consisting of the competence-stimulating peptide (CSP), its membrane-embedded histidine kinase receptor ComD, and the cognate response regulator ComE. Extensive screening of pneumococcal isolates has revealed that two major CSP variants, CSP1 and CSP2, are found in members of this species. Even though the primary structures of CSP1 and CSP2 are about 50% identical, they are highly specific for their respective receptors, ComD1 and ComD2. In the present work, we have investigated the structural basis of this specificity by determining the three-dimensional structure of CSP1 from nuclear magnetic resonance data and comparing the agonist activity of a number of CSP1/CSP2 hybrid peptides toward the ComD1 and ComD2 receptors. Our results show that upon exposure to membrane-mimicking environments, the 17-amino-acid CSP1 pheromone adopts an amphiphilic alpha-helical configuration stretching from residue 6 to residue 12. Furthermore, the pattern of agonist activity displayed by the various hybrid peptides revealed that hydrophobic amino acids, some of which are situated on the nonpolar side of the alpha-helix, strongly contribute to CSP specificity. Together, these data indicate that the identified alpha-helix is an important structural feature of CSP1 which is essential for effective receptor recognition under natural conditions.

(Strept)avidin as Host for Biotinylated Coordination Complexes: Stability, Chiral Discrimination, and Cooperativity

Incorporation of a biotinylated ruthenium tris(bipyridine) [Ru(bpy)(2)(Biot-bpy)](2+) (1) in either avidin or streptavidin-(strept)avidin-can be conveniently followed by circular dichroism spectroscopy. To determine the stepwise association constants, cooperativity, and chiral discrimination properties, diastereopure (Lambda and Delta)-1 species were synthesized and incorporated in tetrameric (strept)avidin to afford (Delta-[Ru(bpy)(2)(Biot-bpy)](2+))(x)() subsetavidin, (Lambda-[Ru(bpy)(2)(Biot-bpy)](2+))(x)() subsetavidin, (Delta-[Ru(bpy)(2)(Biot-bpy)](2+))(x)() subsetstreptavidin, and (Lambda-[Ru(bpy)(2)(Biot-bpy)](2+))(x)() subsetstreptavidin (x = 1-4) For these four systems, the overall stability constants are log beta(4) = 28.6, 30.3, 36.2, and 36.4, respectively. Critical analysis of the CD titrations data suggests a strong cooperativity between the first and the second binding event (x = 1, 2) and a pronounced difference in affinity between avidin and streptavidin for the dicationic guest 1 as well as modest enantiodiscrimination properties with avidin as host.

Semisynthesis of a glycosylated Im7 analogue for protein folding studies

To establish a system to address questions concerning the influence of glycosylation on protein folding pathways, we have developed a semisynthetic route toward the immunity protein Im7. This fourhelix protein has been used extensively as model protein for folding studies. Native chemical ligation (NCL) affords an N-linked chitobiose glycoprotein analogue of Im7 with an Ala29Cys mutation. The semisynthetic approach relies on the solid-phase peptide synthesis (SPPS) of N-terminal thioesters (including helix I), in glycosylated or unglycosylated form, in combination with the expression of the C-terminal fragment of Im7 (containing helices II-IV). Detailed kinetic and thermodynamic analysis of the protein folding behavior reveals that semisynthetic Im7 analogues are well suited for protein folding studies and that the folding mechanism of the glycoprotein of this Im7 variant is not significantly altered over the unglycosylated analogue.

Efficient and Versatile Stereoselective Synthesis of Cryptophycins

The cryptophycins are a family of cyclic depsipeptides with four retrosynthetic units A to D which correspond to the respective amino acids and hydroxy acids. A new synthetic route to unit A allows the selective generation of all four stereogenic centres by introducing two of them in a catalytic asymmetric dihydroxylation, followed by substrate-controlled diastereoselective reactions. The diol also serves as the epoxide precursor. This approach provides selective access to stereoisomers of unit A (enantiomers, epimers) for structure-activity relationship studies. The unit A derivatives were incorporated into cryptophycin-1, cryptophycin-52 and a novel epimer of cryptophycin-52.

Design of a redox-linked active metal site: manganese bound to bacterial reaction centers at a site resembling that of photosystem II

Metals bound to proteins perform a number of crucial biological reactions, including the oxidation of water by a manganese cluster in photosystem II. Although evolutionarily related to photosystem II, bacterial reaction centers lack both a strong oxidant and a manganese cluster for mediating the multielectron and proton transfer needed for water oxidation. In this study, carboxylate residues were introduced by mutagenesis into highly oxidizing reaction centers at a site homologous to the manganese-binding site of photosystem II. In the presence of manganese, light-minus-dark difference optical spectra of reaction centers from the mutants showed a lack of the oxidized bacteriochlorophyll dimer, while the reduced primary quinone was still present, demonstrating that manganese was serving as a secondary electron donor. On the basis of these steady-state optical measurements, the mutant with the highest-affinity site had a dissociation constant of approximately 1 microM. For the highest-affinity mutant, a first-order rate with a lifetime of 12 ms was observed for the reduction of the oxidized bacteriochlorophyll dimer by the bound manganese upon exposure to light. The dependence of the amplitude of this component on manganese concentration yielded a dissociation constant of approximately 1 muM, similar to that observed in the steady-state measurements. The three-dimensional structure determined by X-ray diffraction of the mutant with the high-affinity site showed that the binding site contains a single bound manganese ion, three carboxylate groups (including two groups introduced by mutagenesis), a histidine residue, and a bound water molecule. These reaction centers illustrate the successful design of a redox active metal center in a protein complex.

DNA binding-uptake system: a link between cell-to-cell communication and biofilm formation

DNA has recently been described as a major structural component of the extracellular matrix in biofilms. In streptococci, the competence-stimulating peptide (CSP) cell-to-cell signal is involved in competence for genetic transformation, biofilm formation, and autolysis. Among the genes regulated in response to the CSP are those involved in binding and uptake of extracellular DNA. We show in this study that a functional DNA binding-uptake system is involved in biofilm formation. A comGB mutant of Streptococcus mutans deficient in DNA binding and uptake, but unaffected in signaling, showed reduced biofilm formation. During growth in the presence of DNase I, biofilm was reduced in the wild type to levels similar to those found with the comGB mutant, suggesting that DNA plays an important role in the wild-type biofilm formation. We also showed that growth in the presence of synthetic CSP promoted significant release of DNA, with similar levels in the wild type and in the comGB mutant. The importance of the DNA binding-uptake system in biofilm formation points to possible novel targets to fight infections.

Protein fibers as performance proteins: new technologies and applications

Protein fibers are fundamental building blocks of life playing an essential role in motility, elasticity, scaffolding, stabilization and the protection of cells, tissues and organisms. Despite nearly a century of research into the assembly mechanisms and structures of fibrous proteins, only limited information is still available. Within the past decade, however, insights have been provided into how some fibrous proteins assemble and how they function in biology. In addition, efforts are increasingly being made to employ protein fibers as performance molecules in man-made medical and technical applications.

Relationship between temporary inhibition and structure of disulfide-linkage analogs of marinostatin, a natural ester-linked protein protease inhibitor

A 12-residue marinostatin [MST(1-12): (1)FATMRYPSDSDE(12)] which contains two ester linkages of Thr(3)-Asp(9) and Ser(8)-Asp(11) strongly inhibits subtilisin. In order to study the relationship between the inhibitory activity, structure, and stability of MST, MST analogs were prepared by changing ester linkages to a disulfide linkages. The analogs without the disulfide linkage between 3 and 9 positions lost their inhibitory activity. The K(i) value of 1SS(C(3)-C(9)) ((1)FACMRYPSCSDE(12)), which has a single disulfide linkage of Cys(3)-Cys(9) was comparable with those of MST(1-12) and MST-2SS ((1)FACMRYPCCSCE(12)), a doubly linked analog of Cys(3)-Cys(9) and Cys(8)-Cys(11). However, 1SS(C(3)-C(9)) and MST-2SS showed temporary inhibition, but not MST(1-12): These analogs were inactivated after incubation with subtilisin for 30 min, and were specifically hydrolyzed at the reactive site. (1)H NMR study showed that 1SS(C(3)-C(9)) has two conformations, which contain a cis- (70%) or trans- (30%) Pro residue, while MST-2SS as well as MST(1-12) takes a single conformation containing only a cis-Pro residue. Hydrogen-deuterium exchange rate of the Arg(5) (P1') NH proton of the MST analogs was about 100 times faster than that of MST(1-12). These results indicate that the linkage between the positions 8 and 11 plays a role for fixing the cis-conformation of the Pro(7) residue, and that the linkage between 3 and 9 is indispensable for the inhibition, but not enough for stable protease-inhibitor complex.

Solution structure of marinostatin, a natural ester-linked protein protease inhibitor

Marinostatin is a unique protein protease inhibitor containing two ester linkages. We have purified a 12-residue marinostatin [MST(1-12), (1)FATMRYPSDSDE(12)] and determined the residues involved in the formation of the ester linkages and the solution structure by (1)H NMR spectroscopy and restrained molecular dynamics calculation. The two ester linkages of MST(1-12) are formed between hydroxyl and carboxyl groups, Thr(3)-Asp(9) and Ser(8)-Asp(11), indicating that MST(1-12) has two cyclic regions which are fused at the residues of Ser(8) and Asp(9). A strong NOE cross-peak between Tyr(6) H(alpha) and Pro(7) H(alpha) was observed, indicating that the Pro(7) residue takes a cis-conformation. Well-converged structures and hydrogen-deuterium experiments of MST(1-12) showed that the backbone NH proton of the P1'residue, Arg(5), is hydrogen-bonded to the carbonyl oxygen of the ester linkage between Thr(3) and Asp(9). To reveal the significance of the ester linkages, a marinostatin analogue, MST-2SS ((1)FACMRYPCCSCE(12)) with two disulfide bridges of Cys(3)-Cys(9) and Cys(8)-Cys(11), was also synthesized. The inhibitory activity of MST-2SS was as strong as that of MST(1-12), and the Pro(7) residue of MST-2SS also takes a cis-conformation. However, the exchange rate of the Arg(5) NH proton of MST-2SS was about 100 times faster than that of MST(1-12), and the structure calculation of MST-2SS was not converged on account of the small number of NOEs, indicating that MST-2SS takes a more flexible structure. The hydrogen acceptability of the ester linkage formed by the P2 position residue, Thr(3), is crucial for suppressing the fluctuation of the reactive site and sustaining the inhibitory activity, which enables marinostatin to be one of the smallest protease inhibitors in nature.

TLR2 recognizes a bacterial lipopeptide through direct binding

The TLRs play an important role in the initiation of cellular innate immune responses to a wide range of bacterial products, including LPS and lipoproteins. Although rapid progress has been made on signaling functions of activated TLRs, the molecular mechanisms that lead to TLR activation are still poorly understood. We report in this study that the extracellular domain of TLR2 interacts directly with synthetic bacterial lipopeptide (sBLP), a potent analog of bacterial lipoproteins. Using fluorescently labeled sBLP complexed to soluble recombinant CD14 (rsCD14), we observed specific binding of sBLP to the surface of cells expressing TLR2 transgenes and to a recombinant soluble form of the TLR2 ectodomain. TLR2-mediated binding of sBLP at the cell surface did not require prior induction of intracellular signals. In addition, using a chimeric TLR2/TLR4 construct, we showed that the leucine-rich region of TLR2 carries the specificity for binding of the agonist and for initiating signaling. Specific binding of fluorescent sBLP to purified sTLR2 required sCD14. However, sCD14 was not part of the complex formed by soluble TLR2 and sBLP. Together, these data provide evidence that TLR2 recognizes sBLP through direct binding.

Conformation and activity of delta-lysin and its analogs

Delta-Lysin is a 26-residue hemolytic peptide secreted by Staphylococcus aureus. Unlike the bee venom peptide melittin, delta-lysin does not exhibit antibacterial activity. We have synthesized delta-lysin and several analogs wherein the N-terminal residues of the toxin were sequentially deleted. The toxin has three aspartic acids, four lysines and no prolines. Analogs were also generated in which all the aspartic acids were replaced with lysines. A proline residue was introduced in the native sequences as well as in the analogs where aspartic acids were replaced with lysines. We observed that 20- and 22-residue peptides corresponding to residues 7-26 and 5-26 of delta-lysin, respectively, had greater hemolytic activity than the parent peptide. These shorter peptides, unlike delta-lysin, did not self-associate to adopt alpha-helical conformation in water, at lytic concentrations. Introduction of proline or substitution of aspartic acids by lysines resulted in loss in propensity to adopt helical conformation in water. When proline was introduced in the peptides corresponding to the native toxin sequence, loss of hemolytic activity was observed. Substitution of all the aspartic acids with lysines resulted in enhanced hemolytic activity in all the analogs. However, when both proline and aspartic acid to lysine changes were made, only antibacterial activity was observed in the shorter peptides. Our investigations on delta-lysin and its analogs provide insights into the positioning of anionic, cationic residues and proline in determining hemolytic and antibacterial activities.

Design of novel analogues with potent antibiotic activity based on the antimicrobial peptide, HP(2-9)-ME(1-12)

To develop novel antibiotic peptides useful as therapeutic drugs, a number of analogues were designed to increase the hydrophobic helix region either by Trp-substitution or net positive charge increase by Lys-substitution, from HP(2-9)-ME(1-12). The antibiotic activities of these peptides were evaluated using bacterial (Salmonella tryphimurium, Proteus vulgaris, Bacillus subtilis and Staphylococcus aureus), fungi (Saccharomyces cerevisiae, Trichosporon beigelii and Candida albicans), tumor and human erythrocyte cells. The substitution of Lys for Thr at position 18 and 19 of HP(2-9)-ME(1-12) (HM5) increased activity against Proteus vulgaris and fungal strains without hemolysis. In contrast, substitution of Trp for Lys and Thr at positions 2, 15 and 19 of HP(2-9)-ME(1-12), respectively (HM3 and HM4), decreased activity but increased hemolysis against human erythrocytes. This suggests that an increase in positive charge increases antimicrobial activity whereas an increase in hydrophobicity by introducing Trp residues at C-terminus of HP(2-9)-ME(1-12) causes a hemolytic effect. Circular dichroism spectra suggested that the alpha-helical structure of these peptides plays an important role in their antibiotic effect but that the alpha-helical property is not connected with the enhanced antibiotic activity.

Mechanisms of protein fluorophore formation and engineering

Green fluorescent protein (GFP) from the jellyfish Aequorea victoria and GFP-like proteins from Anthozoa species contain light-absorbing chromophores within their protein sequences. Recent studies have made progress in obtaining bright variants of these proteins that develop chromophores quickly and efficiently, as well as novel fluorescent proteins that photoconvert (i.e. change color upon illumination at specific wavelengths). Further molecular characterization of the structure and maturation of these proteins is in progress, aimed at providing information for rational design of variants with desired fluorescence properties.

Biofilm mode of growth of Streptococcus intermedius favored by a competence-stimulating signaling peptide

Gram-positive and gram-negative bacteria use quorum sensing to coordinate population behavior. In several streptococci, quorum sensing mediated by competence-stimulating peptides (CSP) is associated with development of competence for transformation. We show here that a synthetic CSP favored the biofilm mode of growth of Streptococcus intermedius without affecting the rate of culture growth.

Differential Immune Responses and Protective Efficacy Induced by Components of a Tuberculosis Polyprotein Vaccine, Mtb72F, Delivered as Naked DNA or Recombinant Protein

Key Ags of Mycobacterium tuberculosis initially identified in the context of host responses in healthy purified protein derivative-positive donors and infected C57BL/6 mice were prioritized for the development of a subunit vaccine against tuberculosis. Our lead construct, Mtb72F, codes for a 72-kDa polyprotein genetically linked in tandem in the linear order Mtb32(C)-Mtb39-Mtb32(N). Immunization of C57BL/6 mice with Mtb72F DNA resulted in the generation of IFN-gamma responses directed against the first two components of the polyprotein and a strong CD8(+) T cell response directed exclusively against Mtb32(C). In contrast, immunization of mice with Mtb72F protein formulated in the adjuvant AS02A resulted in the elicitation of a moderate IFN-gamma response and a weak CD8(+) T cell response to Mtb32c. However, immunization with a formulation of Mtb72F protein in AS01B adjuvant generated a comprehensive and robust immune response, resulting in the elicitation of strong IFN-gamma and Ab responses encompassing all three components of the polyprotein vaccine and a strong CD8(+) response directed against the same Mtb32(C) epitope identified by DNA immunization. All three forms of Mtb72F immunization resulted in the protection of C57BL/6 mice against aerosol challenge with a virulent strain of M. tuberculosis. Most importantly, immunization of guinea pigs with Mtb72F, delivered either as DNA or as a rAg-based vaccine, resulted in prolonged survival (>1 year) after aerosol challenge with virulent M. tuberculosis comparable to bacillus Calmette-Guérin immunization. Mtb72F in AS02A formulation is currently in phase I clinical trial, making it the first recombinant tuberculosis vaccine to be tested in humans.

Cytotoxicity responses to peptide antigens in rheumatoid arthritis and ankylosing spondylitis

OBJECTIVE

To measure levels of IgG antibodies against structurally related synthetic peptides of HLA-DRB1*0404, type XI collagen, and Proteus mirabilis in patients with rheumatoid arthritis (RA) and HLA-B*2705 and Klebsiella pneumoniae in patients with ankylosing spondylitis (AS), and to determine whether sera from RA and AS patients are cytotoxic for sheep red blood cells (SRBC) coated with HLA-DRB1*0404, type XI collagen, or HLA-B*2705.

METHODS

Sera from 51 patients with RA, 34 with AS, and 38 healthy controls were tested against synthetic EQRRAA, ESRRAL, LRREI, and IRRET peptides by ELISA. Sera from patients and controls were also tested for reactivity in complement mediated cytotoxicity with SRBC coated with EQRRAA and HLA-B*2705, LRREI peptides.

RESULTS

Antibodies to synthetic peptides containing EQRRAA, ESRRAL, LRREI, and IRRET were significantly increased in RA patients compared with AS patients (p < 0.001) and controls (p < 0.001). The percentage lysis data for SRBC coated with EQRRAA and LRREI peptides were significantly higher for RA sera (p < 0.001) compared to control sera. Percentage lysis for SRBC coated with HLA-B*2705 peptide was significantly higher for AS sera (p < 0.001) compared to control sera.

CONCLUSION

Our results suggest that antibodies against antigenic determinants of P. mirabilis in RA and K. pneumoniae in AS have cytotoxic properties on structurally related host proteins. These cytotoxic antibodies together with T cell interactions could be relevant in the etiopathogenesis of RA and AS.

Genetically engineered silk-elastinlike protein polymers for controlled drug delivery

The silk-elastinlike class of genetically engineered protein polymers is composed of tandemly repeated silk-like (Gly-Ala-Gly-Ala-Gly-Ser) and elastin-like (Gly-Val-Gly-Val-Pro) amino acid blocks. The precision with which these polymers can be synthesized, as well as the ability to incorporate motifs that allow for gel-formation, stimuli-sensitivity, biodegradation, and biorecognition have stimulated interest in their use for controlled drug and gene delivery. This review will focus on the synthesis and characterization of silk-elastinlike polymers as related to controlled drug delivery. The design and biological synthesis of the copolymers, by recombinant DNA techniques, are reviewed. The characterization of the polymers is discussed. Finally, biocompatibility of the polymers and recent studies to determine their potential utility for controlled drug and gene delivery are reviewed.

Genetically engineered silk-elastinlike protein polymers for controlled drug delivery

The silk-elastinlike class of genetically engineered protein polymers is composed of tandemly repeated silk-like (Gly-Ala-Gly-Ala-Gly-Ser) and elastin-like (Gly-Val-Gly-Val-Pro) amino acid blocks. The precision with which these polymers can be synthesized, as well as the ability to incorporate motifs that allow for gel-formation, stimuli-sensitivity, biodegradation, and biorecognition have stimulated interest in their use for controlled drug and gene delivery. This review will focus on the synthesis and characterization of silk-elastinlike polymers as related to controlled drug delivery. The design and biological synthesis of the copolymers, by recombinant DNA techniques, are reviewed. The characterization of the polymers is discussed. Finally, biocompatibility of the polymers and recent studies to determine their potential utility for controlled drug and gene delivery are reviewed.

Cutting edge: role of Toll-like receptor 1 in mediating immune response to microbial lipoproteins

The Toll-like receptor (TLR) family acts as pattern recognition receptors for pathogen-specific molecular patterns (PAMPs). TLR2 is essential for the signaling of a variety of PAMPs, including bacterial lipoprotein/lipopeptides, peptidoglycan, and GPI anchors. TLR6 associates with TLR2 and recognizes diacylated mycoplasmal lipopeptide along with TLR2. We report here that TLR1 associates with TLR2 and recognizes the native mycobacterial 19-kDa lipoprotein along with TLR2. Macrophages from TLR1-deficient (TLR1(-/-)) mice showed impaired proinflammatory cytokine production in response to the 19-kDa lipoprotein and a synthetic triacylated lipopeptide. In contrast, TLR1(-/-) cells responded normally to diacylated lipopeptide. TLR1 interacts with TLR2 and coexpression of TLR1 and TLR2 enhanced the NF-kappaB activation in response to a synthetic lipopeptide. Furthermore, lipoprotein analogs whose acylation was modified were preferentially recognized by TLR1. Taken together, TLR1 interacts with TLR2 to recognize the lipid configuration of the native mycobacterial lipoprotein as well as several triacylated lipopeptides.

In vivo effects of a synthetic 2-kilodalton macrophage-activating lipopeptide of Mycoplasma fermentans after pulmonary application

Mycoplasmas can cause interstitial pneumonias inducing critical illness in humans and animals. Mycoplasma infections are characterized by an influx of neutrophils, followed by an accumulation of macrophages and lymphocytes. The present study deals with the question of which mycoplasmal components cause this host reaction. The mycoplasma-derived, macrophage-activating lipopeptide 2S-MALP-2 was used to mimic the sequelae of a mycoplasma infection. To this end, 2S-MALP-2 was intratracheally instilled into the lungs of Lewis rats, and the bronchoalveolar lavage cells were examined at different times after different doses of 2S-MALP-2. Application of 2.5 microg induced a pronounced leukocyte accumulation in the bronchoalveolar space. At 24 h after 2S-MALP-2 administration, the majority of leukocytes consisted of neutrophils, followed by macrophages, peaking on days 2 and 3. Lymphocyte numbers, although amounting to only a few percent of the total bronchoalveolar lavage cells, also increased significantly, with maximal lymphocyte accumulation occurring by 72 h after instillation. The leukocyte count of the lung interstitium was increased on day 3 after treatment. After 10 days all investigated cell populations returned to control levels. Transient chemotactic activity for neutrophils was detected in the bronchoalveolar lavage fluid early after 2S-MALP-2 application, followed by monocyte chemoattractant protein-1 activity (MCP-1) in lung homogenates. MCP-1 was produced by bronchoalveolar lavage cells upon stimulation with 2S-MALP-2. Our data indicate that mycoplasmal lipoproteins and lipopeptides are probably the most relevant mycoplasmal components for the early host reaction. The primary target cells are likely to be the alveolar macrophages liberating chemokines, which attract further leukocytes.

Total chemical synthesis of a 27 kDa TASP protein derived from the MscL ion channel of M. tuberculosis by ketoxime-forming ligation

A 27-kDa TASP protein, T(5)Msc(103-151), that was derived from the cytoplasmic domain (amino acid residues 103-151) of the MscL ion channel of M. tuberculosis was synthesized by ketoxime-forming chemoselective ligation between a template molecule carrying five pyruvic acid groups, and linear channel peptides carrying one aminooxyacetic acid group. Ketoxime-forming ligation provided for highly efficient assembly of this large totally synthetic protein construct with yields >90% with modest excess (1.5x) of the aminooxy peptide. Formation of the desired TASP molecule was confirmed by SDS-PAGE analysis and MALDI mass spectrometry. The effect of template attachment on the structure of the peptides constituting the TASP was assessed by circular dichroism spectroscopy. Attachment of the peptides to the topological template induces predominantly helical secondary structure, whereas an analogous peptide that did not bear an aminooxy group, MscL(103-151), does not exhibit significant secondary structure at pH 7 and is found to be monomeric in concentrations up to 65 microM. This observation can be explained by entropic destabilization of the unfolded state of T(5)Msc(103-151) due to the attachment to the template and the resulting loss of degrees of freedom. Pyruvic acid-based ketoxime-forming chemoselective ligation may thus prove to be a useful tool for the assembly of large, non-native protein constructs and their biophysical study.

Role of the core region of the PufX protein in inhibition of reconstitution of the core light-harvesting complexes of Rhodobacter sphaeroides and Rhodobacter capsulatus

PufX, the protein encoded by the pufX gene of Rhodobacter capsulatus and Rhodobacter sphaeroides, has been further characterized. The mature forms of these proteins contain 9 and 12 fewer amino acids, respectively, at the C-terminal end of the protein than are encoded by their pufX genes. To identify the portion of PufX responsible for inhibition of LH1 formation in reconstitution experiments, different regions (N-terminus and several core regions containing different lengths of the C-terminus) of Rb. sphaeroides and Rb. capsulatus PufX were chemically synthesized. Neither the N- nor C-terminal polypeptides of Rb. sphaeroides were inhibitory to LH1 reconstitution. However, all core segments were active, causing 50% inhibition at a concentration ratio of between 3:1 and 6:1 relative to the LH1 alpha-polypeptides whose concentrations were 3-4 microM. CD measurements indicated that the core segment containing 39 amino acids of Rb. sphaeroides PufX exhibited 47% alpha-helix in trifluoroethanol while the core segment containing 43 amino acids of Rb. capsulatus PufX exhibited 59 and 55% alpha-helix in trifluoroethanol and in 0.80% octylglucoside in water, respectively. Approximately 50% alpha-helix was also indicated by a PHD (Burkhard-Rost) structure prediction. Binding of bacteriochlorophyll to these PufX core segments is implicated.

Synthesis of peptides and proteins without cysteine residues by native chemical ligation combined with desulfurization

The highly chemoselective reaction between unprotected peptides bearing an N-terminal Cys residue and a C-terminal thioester enables the total and semi-synthesis of complex polypeptides. Here we extend the utility of this native chemical ligation approach to non-cysteine containing peptides. Since alanine is a common amino acid in proteins, ligation at this residue would be of great utility. To achieve this goal, a specific alanine residue in the parent protein is replaced with cysteine to facilitate synthesis by native chemical ligation. Following ligation, selective desulfurization of the resulting unprotected polypeptide product with H(2)/metal reagents converts the cysteine residue to alanine. This approach, which provides a general method to prepare alanyl proteins from their cysteinyl forms, can be used to chemically synthesize a variety of polypeptides, as demonstrated by the total chemical syntheses of the cyclic antibiotic microcin J25, the 56-amino acid streptococcal protein G B1 domain, and a variant of the 110-amino acid ribonuclease, barnase.

Dramatic structural and thermodynamic consequences of repacking a protein's hydrophobic core

BACKGROUND

Rop is an RNA binding, dimeric, four-helix bundle protein with a well-defined, regular hydrophobic core ideally suited for redesign studies. A family of Rop variants in which the hydrophobic core was systematically redesigned has previously been created and characterized.

RESULTS

We present a structural and thermodynamic analysis of Ala2Ile2-6, a variant of Rop with an extensively redesigned hydrophobic core. The structure of Ala2Ile2-6 reveals a completely new fold formed by a conformational "flip" of the two protomers around the dimeric interface. The free-energy profile of Ala2Ile2-6 is also very different from that of wild-type Rop. Ala2Ile2-6 has a higher melting temperature than Rop, but undergoes a slightly smaller free-energy change on unfolding.

CONCLUSIONS

The structure of Ala2Ile2-6, along with molecular modeling results, demonstrate the importance of tight packing of core residues and the adoption of favorable core side chain rotamer values in determining helix-helix interactions in the four-helix bundle fold. Structural disorder at the N and C termini of Ala2Ile2-6 provides a basis for the large differences in the enthalpy and entropy of Ala2Ile2-6 folding compared with wildtype Rop.

Microbial lipopeptides induce the production of IL-17 in Th cells

Naive Th cells can be directed in vitro to develop into Th1 or Th2 cells by IL-12 or IL-4, respectively. In vivo, chronic immune reactions lead to polarized Th cytokine patterns. We found earlier that Borrelia burgdorferi, the spirochaete that causes Lyme disease, induces Th1 development in alpha beta TCR-transgenic Th cells. Here, we used TCR-transgenic Th cells and oligonucleotide arrays to analyze the differences between Th1 cells induced by IL-12 vs those induced by B. burgdorferi. Transgenic Th cells primed with peptide in the presence of B. burgdorferi expressed several mRNAs, including the mRNA encoding IL-17, at significantly higher levels than Th cells primed with peptide and IL-12. Cytometric single-cell analysis of Th cell cytokine production revealed that IL-17 cannot be categorized as either Th1 or Th2 cytokine. Instead, almost all IL-17-producing Th cells simultaneously produced TNF-alpha and most IL-17(+) Th cells also produced GM-CSF. This pattern was also observed in humans. Th cells from synovial fluid of patients with Lyme arthritis coexpressed IL-17 and TNF-alpha upon polyclonal stimulation. The induction of IL-17 production in Th cells is not restricted to B. burgdorferi. Priming of TCR-transgenic Th cells in the presence of mycobacterial lysates also induced IL-17/TNF-alpha coproduction. The physiological stimulus for IL-17 production was hitherto unknown. We show here for the first time that microbial stimuli induce the expression of IL-17 together with TNF-alpha in both murine and human T cells. Chronic IL-17 expression induced by microbes could be an important mediator of infection-induced immunopathology.

Activation of toll-like receptor 2 on human dendritic cells triggers induction of IL-12, but not IL-10

Mammalian Toll-like receptors (TLRs) are required for cell activation by bacterial lipoproteins (bLP) and LPS. Stimulation of monocytes with bLP and LPS results in a TLR-dependent induction of immunomodulatory genes leading to the production of pro-inflammatory cytokines. In this paper, we compared the expression and response of TLRs on monocytes and dendritic cells (DC). TLR2, but not TLR4, was detected on peripheral blood monocytes and DC, in lymphoid tissue CD1alpha+ DC as well as on in vitro monocyte-derived DC. Upon stimulation with bLP or LPS, monocytes produced IL-12 and IL-10 at similar levels, whereas monocyte-derived DC produced comparable levels of IL-12, but little IL-10. Greater than 90% of the bLP-induced production of IL-12 was blocked by anti-TLR2 mAb. Thus, DC express TLR2 and activation of this receptor by bLP provides an innate mechanism by which microbial pathogens preferentially activate cell-mediated immunity.

New multi-determinant strategy for a group A streptococcal vaccine designed for the Australian Aboriginal population

Infection with group A streptococci can result in acute and post-infectious pathology, including rheumatic fever and rheumatic heart disease. These diseases are associated with poverty and are increasing in incidence, particularly in developing countries and amongst indigenous populations, such as Australia's Aboriginal population, who suffer the highest incidence worldwide. Immunity to group A streptococci is mediated by antibodies against the M protein, a coiled-coil alpha helical surface protein of the bacterium. Vaccine development faces two substantial obstacles. Although opsonic antibodies directed against the N terminus of the protein are mostly responsible for serotypic immunity, more than 100 serotypes exist. Furthermore, whereas the pathogenesis of rheumatic fever is not well understood, increasing evidence indicates an autoimmune process. To develop a suitable vaccine candidate, we first identified a minimum, helical, non-host-cross-reactive peptide from the conserved C-terminal half of the protein and displayed this within a non-M-protein peptide sequence designed to maintain helical folding and antigenicity, J14 (refs. 8,9). As this region of the M protein is identical in only 70% of group A streptococci isolates, the optimal candidate might consist of the conserved determinant with common N-terminal sequences found in communities with endemic group A streptococci. We linked seven serotypic peptides with J14 using a new chemistry technique that enables the immunogen to display all the individual peptides pendant from an alkane backbone. This construct demonstrated excellent immunogenicity and protection in mice.