Discovery and SAR of isonicotinamide BACE-1 inhibitors that bind beta-secretase in a N-terminal 10s-loop down conformation

A series of low-molecular weight 2,6-diamino-isonicotinamide BACE-1 inhibitors containing an amine transition-state isostere were synthesized and shown to be highly potent in both enzymatic and cell-based assays. These inhibitors contain a trans-S,S-methyl cyclopropane P(3) which bind BACE-1 in a 10s-loop down conformation giving rise to highly potent compounds with favorable molecular weight and moderate to high susceptibility to P-glycoprotein (P-gp) efflux.     

Avian Clock gene polymorphism: evidence for a latitudinal cline in allele frequencies

In comparison with most animal behaviours, circadian rhythms have a well-characterized molecular genetic basis. Detailed studies of circadian clock genes in 'model' organisms provide a foundation for interpreting the functional and evolutionary significance of polymorphic circadian clock genes found within free-living animal populations. Here, we describe allelic variation in a region of the avian Clock orthologue which encodes a functionally significant polyglutamine repeat (ClkpolyQcds), within free-living populations of two passerine birds, the migratory bluethroat (Luscinia svecica) and the predominantly nonmigratory blue tit (Cyanistes caeruleus). Multiple ClkpolyQcds alleles were found within populations of both species (bluethroat: 12 populations, 7 alleles; blue tit: 14 populations, 9 alleles). Some populations of both species were differentiated at the ClkpolyQcds locus as measured by F(ST) and R(ST) values. Among the blue tit, but not bluethroat populations, we found evidence of latitudinal clines in (i) mean ClkpolyQcds repeat length, and (ii) the proportions of three ClkpolyQcds genotype groupings. Parallel analyses of microsatellite allele frequencies, which are considered to reflect selectively neutral processes, indicate that interpopulation allele frequency variation at the ClkpolyQcds and microsatellite loci does not reflect the same underlying demographic processes. The possibility that the observed interpopulation ClkpolyQcds allele frequency variation is, at least in part, maintained by selection for microevolutionary adaptation to photoperiodic parameters correlated with latitude warrants further study.     

A distal methyl substituent attenuates mitochondrial protein synthesis inhibition in oxazolidinone antibacterials

Oxazolidinone analogs bearing substituted piperidine or azetidine C-rings are described. Analogs with a methyl group at the 3-position of the azetidine ring or the 4-position of the piperidine ring exhibited reduced mitochondrial protein synthesis inhibition while retaining good antibacterial potency.     

Complex interactions with females and rival males limit the evolution of sperm offence and defence

Postcopulatory sexual selection favours males which are strong offensive and defensive sperm competitors. As a means of identifying component traits comprising each strategy, we used an experimental evolution approach. Separate populations of Drosophila melanogaster were selected for enhanced sperm offence and defence. Despite using a large outbred population and evidence of substantive genetic variation for each strategy, neither trait responded to selection in the two replicates of this experiment. Recent work with fixed chromosome lines of D. melanogaster suggests that complex genotypic interactions between females and competing males contribute to the maintenance of this variation. To determine whether such interactions could explain our lack of response to selection on sperm offence and defence, we quantified sperm precedence across multiple sperm competition bouts using an outbred D. melanogaster population exhibiting continuous genetic variation. Both offensive and defensive sperm competitive abilities were found to be significantly repeatable only across matings involving ejaculates of the same pair of males competing within the same female. These repeatabilities decreased when the rival male stayed the same but the female changed, and they disappeared when both the rival male and the female changed. Our results are discussed with a focus on the complex nature of sperm precedence and the maintenance of genetic variation in ejaculate characteristics.     

Putative type IV secretion genes in Bacillus anthracis

Although the physiology of Bacillus anthracis, the causative agent of anthrax, has been studied extensively, we still do not know how toxins are dispatched from the bacterial cell. Here, by means of distant homology and genome context analyses, we identify genes encoding putative type IV secretion system-related elements on the B. anthracis plasmids pXO1 and pXO2 and in the chromosome. We argue that this type IV secretion system-like system could be responsible for anthrax toxin secretion, although we also discuss the possibilities of its involvement in the processes of sporulation, germination or conjugation.     

Catenins: playing both sides of the synapse

Synapses of the central nervous system (CNS) are specialized cell-cell junctions that mediate intercellular signal transmission from one neuron to another. The directional nature of signal relay requires synaptic contacts to be morphologically asymmetric with distinct protein components, while changes in synaptic communication during neural network formation require synapses to be plastic. Synapse morphology and plasticity require a dynamic actin cytoskeleton. Classical cadherins, which are junctional proteins associated with the actin cytoskeleton, localize to synapses and regulate synaptic adhesion, stability and remodeling. The major intracellular components of cadherin junctions are the catenin proteins, and increasing evidence suggests that cadherin-catenin complexes modulate an array of synaptic processes. Here we review the role of catenins in regulating the development of pre- and postsynaptic compartments and function in synaptic plasticity, with particular focus on their role in regulating the actin cytoskeleton.     

Electron tomography of viruses

Understanding the molecular architectures of enveloped and complex viruses is a challenging frontier in structural biology. In these viruses, the structural and compositional variation from one viral particle to another generally precludes the use of either crystallization or image averaging procedures that have been successfully implemented in the past for highly symmetric viruses. While advances in cryo electron tomography of unstained specimens provide new opportunities for identification and molecular averaging of individual subcomponents such as the surface glycoprotein spikes on purified viruses, electron tomography of stained and plunge-frozen cells is being used to visualize the cellular context of viral entry and replication. Here, we review recent developments in both areas as they relate to our understanding of the biology of heterogeneous and pleiomorphic viruses.     

The E3 ligase AtCHIP ubiquitylates FtsH1, a component of the chloroplast FtsH protease, and affects protein degradation in chloroplasts

The Arabidopsis E3 ligase AtCHIP was found to interact with FtsH1, a subunit of the chloroplast FtsH protease complex. FtsH1 can be ubiquitylated by AtCHIP in vitro, and the steady-state level of FtsH1 is reduced in AtCHIP-over-expressing plants under high-intensity light conditions, suggesting that the ubiquitylation of FtsH1 by AtCHIP might lead to the degradation of FtsH1 in vivo. Furthermore, the steady-state level of another subunit of the chloroplast FtsH protease complex, FtsH2, is also reduced in AtCHIP-over-expressing plants under high-intensity light conditions, and FtsH2 interacts physically with AtCHIP in vivo, suggesting the possibility that FtsH2 is also a substrate protein for AtCHIP in plant cells. A substrate of FtsH protease in vivo, the photosystem II reaction center protein D1, is not efficiently removed by FtsH in AtCHIP-over-expressing plants under high-intensity light conditions, supporting the assumption that FtsH subunits are substrates of AtCHIP in vivo, and that AtCHIP over-expression may lead to a reduced level of FtsH in chloroplasts. AtCHIP interacts with cytosolic Hsp70 and the precursors of FtsH1 and FtsH2 in the cytoplasm, and Hsp70 also interacts with FtsH1, and these protein-protein interactions appear to be increased under high-intensity light conditions, suggesting that Hsp70 might be partly responsible for the increased degradation of the substrates of Hsp70, such as FtsH1 and FtsH2, in AtCHIP-over-expressing plants under high-intensity light conditions. Therefore, AtCHIP, together with Hsp70, may play an important role in protein quality control in chloroplasts.     

Potent and selective biphenyl azole inhibitors of adipocyte fatty acid binding protein (aFABP)

Herein we report the first disclosure of biphenyl azoles that are nanomolar binders of adipocyte fatty acid binding protein (aFABP or aP2) with up to thousand-fold selectivity against muscle fatty acid binding protein and epidermal fatty acid binding protein. In addition a new radio-ligand to determine binding against the three fatty acid binding proteins was also synthesized.