Protein misfolding is related to some fatal diseases including Alzheimer's disease (AD). Amyloid beta-peptide (Abeta) generated from amyloid precursor protein can aggregate into amyloid fibrils, which are known to be a major component of Abeta deposits (senile plaques). The fibril formation of Abeta is typical of a nucleation-dependent process through self-recognition. Moreover, during fibrillization, several metastable intermediates such as soluble oligomers, including Abeta-derived diffusible ligands (ADDLs) and Abeta*56, are produced, which are thought to be the most toxic species to neuronal cells. Therefore, construction of molecules that decrease the Abeta aggregates, including soluble oligomers, protofibrils, and amyloid fibrils, might further our understanding of the mechanism(s) behind fibril formation and enable targeted drug discovery against AD. To this aim, various peptides and peptide derivatives have been constructed using the "Abeta binding element" based on the structural models of Abeta amyloid fibrils and the mechanisms of self-assembly. The central hydrophobic amino acid sequence, LVFF, of Abeta is a key sequence to self-assemble into amyloid fibrils. By combination of this core sequence with a hydrophobic or hydrophilic moiety, such as cholic acid or aminoethoxy ethoxy acetic acid units, respectively, good inhibitors of Abeta aggregation can be designed and synthesized. A peptide, LF, consisting of the sequence Ac-KQKLLLFLEE-NH 2, was designed based on the core sequence of Abeta but with a simplified amino acid sequence. The LF peptide can form amyloid-like fibrils that efficiently coassemble with mature Abeta1-42 fibrils. The LF peptide was also observed to immediately transform the soluble oligomers of Abeta1-42, which are thought to pose toxicity in AD, into amyloid-like fibrils. On the other hand, two Abeta-like beta-strands with a parallel orientation were embedded in green fluorescent protein (GFP), comprised of a beta-barrel structure, to make pseudo-Abeta beta-sheets on its surface. The GFP variant P13H binds to Abeta1-42 and inhibits Abeta1-42 oligomerization effectively in a substoichiometric condition. Thus, molecules capable of binding to Abeta can be designed based on structural similarities with the Abeta molecule. The peptide and protein mimetics based on the structural features of Abeta might lead to the development of drug candidates against AD.

Anhydrobiotic (i.e., life without water) organisms are known to produce group 3 late embryogenesis abundant (G3LEA) proteins during adaptation to severely water-deficient conditions. Their primary amino acid sequences are composed largely of loosely conserved 11-mer repeat units. However, little information has been obtained for the structural and functional roles of these repeat units. In this study, we first explore the consensus sequences of the 11-mer repeat units for several native G3LEA proteins originating from anhydrobiotic organisms among insects (Polypedilum vanderplanki), nematodes, and plants. Next, we synthesize four kinds of model peptides (LEA models), each of which consists of four or two repeats of the 11-mer consensus sequences for each of the three organisms. The structural and thermodynamic properties of the LEA models were examined in solution, in dehydrated and rehydrated states, and furthermore in the presence of trehalose, since a great quantity of this sugar is known to be produced in the dried cells of most anhydrobiotic organisms. The results of Fourier transform infrared (FTIR) spectroscopic measurements indicate that all of the LEA models transform from random coils to alpha-helical coiled coils on dehydration and return to random coils again on rehydration, both with and without trehalose. In contrast, such structural changes were never observed for a control peptide with a randomized amino acid sequence. Furthermore, our differential scanning calorimetry (DSC) measurements provide the first evidence that the above 11-mer motif-containing peptides themselves vitrify with a high glass transition temperature (>100 degrees C) and a low enthalpy relaxation rate. In addition, they play a role in reinforcing the glassy matrix of the coexisting trehalose. On the basis of these results, we discuss the underlying mechanism of G3LEA proteins as desiccation stress protectants.

BackgroundBotulinum neurotoxins (BoNT) are a family of category A select bioterror agents and the most potent biological toxins known. Cloned antibody therapeutics hold considerable promise as BoNT therapeutics, but the therapeutic utility of antibodies that bind the BoNT light chain domain (LC), a metalloprotease that functions in the cytosol of cholinergic neurons, has not been thoroughly explored.Methods and FindingsWe used an optimized hybridoma method to clone a fully human antibody specific for the LC of serotype A BoNT (BoNT/A). The 4LCA antibody demonstrated potent in vivo neutralization when administered alone and collaborated with an antibody specific for the HC. In Neuro-2a neuroblastoma cells, the 4LCA antibody prevented the cleavage of the BoNT/A proteolytic target, SNAP-25. Unlike an antibody specific for the HC, the 4LCA antibody did not block entry of BoNT/A into cultured cells. Instead, it was taken up into synaptic vesicles along with BoNT/A. The 4LCA antibody also directly inhibited BoNT/A catalytic activity in vitro.ConclusionsAn antibody specific for the BoNT/A LC can potently inhibit BoNT/A in vivo and in vitro, using mechanisms not previously associated with BoNT-neutralizing antibodies. Antibodies specific for BoNT LC may be valuable components of an antibody antidote for BoNT exposure.

CrylAa toxin-binding proteins from the midgut brush border membrane vesicles of Bombyx mori, a toxin-susceptible silkworm, were analyzed to find candidates for the toxin receptors. Ligand blotting showed that CrylAa toxin bound to a 120-kDa protein. A part of the 120-kDa protein was solubilized from the membrane vesicles with phosphatidylinositol-specific phospholipase C, resulting in a 110-kDa protein which therefore may be linked to a glycosyl-phosphatidylinositol anchor. The 120-kDa and 110-kDa Cryl Aa toxin-binding proteins were solubilized with detergent or pohosphatidylinositol-specific phospholipase C, respectively, and purified using anion-exchange chromatography. Scatchard plot analysis for the specific binding of purified 110-kDa protein to Cryl Aa toxin yielded a Kd value of 7.6 nM, which was similar to that for the binding of intact brush border membrane vesicles to the toxin. N-terminal and internal amino acid sequences of the 120-kDa and 110-kDa proteins showed high degrees of similarity to those of aminopeptidase N, a putative CrylAc toxin receptor, reported in Munducu sexta and Heliothis virescens. On this basis, the 120-kDa CrylAa toxin-binding protein from B. mori was identified as a member of the aminopeptidase family.Keywords: Bacillus thuringiensis; S-endotoxin ; Bombyx mori; receptor; aminopeptidase N.Bacillus thuringiensis, a gram-positive bacterium, produces various types of insecticidal proteinaceous crystal inclusions during spomlation [l-31. When this bacterium is ingested by susceptible insects, these crystal inclusions, composed of protoxins [4], are solubilized in the alkaline environment of the insect midgut and processed proteolytically to yield smaller active toxins [3, 51. The toxin is believed to bind specifically to receptor molecules on the midgut epithelial cells of host insects [7-101, disrupting the ion permeability of midgut cell membranes [ll]. This results in a net influx of ions and an accompanying influx of water, so that the cells swell and lyse [6, 121. The formation of cation-selective [13-151 or small non-specific [16] pores in the membrane has been proposed as a possible mechanism of the toxin action [17].Each toxin shows a specific insecticidal spectrum in vivo. In some cases, this activity spectrum correlates with the presence of specific toxin receptors in the brush border membrane vesicles (BBMV) [7][8][9][10] 181, while in other cases the binding of the toxin to the BBMV was unrelated to in vivo toxic activity. In the latter cases, toxin bound to BBMV, but very low-level in vivo toxicity resulted [18, 191. Although the binding of toxin to specific receptors on the midgut epithelial cells may be one of the requirements for the insecticidal activity in vivo, other factors, such as the ability of the toxin to interact with the epithelium membrane lipid layer, might also be involved. However, it is not clear what the normal function of the receptor molecules might be or how these molecules are involved in toxin action. Insects are able to acquire resistance to ...

A virus with isometric virus particles (ca. 25 nm) was isolated from an apple tree and named Apple latent spherical virus (ALSV). Virus particles purified from infected Chenopodium quinoa formed two bands with densities of 1n41 and 1n43 g/cm 3 in CsCl equilibrium density-gradient centrifugation, indicating that the virus is composed of two components. The virus had two ssRNA species (RNA1 and RNA2) and three capsid proteins (Vp25, Vp24 and Vp20). The complete nucleotide sequences of RNA1 and RNA2 were determined to be 6815 nt and 3384 nt excluding the 3h poly (