The 1.6 A crystal structure of the catalytic domain of PlyB, a bacteriophage lysin active against Bacillus anthracis

Lysins are peptidoglycan hydrolases that are produced by bacteriophage and act to lyse the bacterial host cell wall during progeny phage release. Here, we describe the structure and function of a novel bacteriophage-derived lysin, PlyB, which displays potent lytic activity against the Bacillus anthracis-like strain ATCC 4342. This molecule comprises an N-terminal catalytic domain (PlyB(cat)) and a C-terminal bacterial SH3-like domain, SH3b. It is shown that both domains are required for effective catalytic activity against ATCC 4342. Further, PlyB has specific activity comparable to the phage lysin PlyG, an amidase being developed as a therapeutic against anthrax. In contrast to PlyG, however, the 1.6 A X-ray crystal structure of PlyB(cat) reveals that the catalytic domain adopts the glycosyl hydrolase (GH)-25, rather than phage T7 lysozyme-like fold. PlyB therefore represents a new class of anthrax lysin and a new defensive tool in the armament against anthrax-mediated bioterrorism.     

GroEL recognises sequential and non-sequential linear structural motifs compatible with extended beta-strands and alpha-helices.

The chaperonin GroEL binds a variety of polypeptides that share no obvious sequence similarity. The precise structural, chemical and dynamic features that are recognised remain largely unknown. Structural models of the complex between GroEL and its co-chaperonin GroES, and of the isolated apical domain of GroEL (minichaperone; residues 191-376) with a 17 residue N-terminal tag show that a linear sequential sequence (extended beta-strand) can be bound. We have analysed characteristics of the motifs that bind to GroEL by using affinity panning of immobilised GroEL minichaperones for a library of bacteriophages that display the fungal cellulose-binding domain of the enzyme cellobiohydrolase I. This protein has seven non-sequential residues in its binding site that form a linear binding motif with similar dimensions and characteristics to the peptide tag that was bound to the minichaperone GroEL(191-376). The seven residues thus form a constrained scaffold. We find that GroEL does bind suitable mutants of these seven residues. The side-chains recognised do not have to be totally hydrophobic, but polar and positively charged chains can be accommodated. Further, the spatial distribution of the side-chains is also compatible with those in an alpha-helix. This implies that GroEL can bind a wide range of structures, from extended beta-strands and alpha-helices to folded states, with exposed side-chains. The binding site can accommodate substrates of approximately 18 residues when in a helical or seven when in an extended conformation. The data support two activities of GroEL: the ability to act as a temporary parking spot for sticky intermediates by binding many motifs; and an unfolding activity of GroEL by binding an extended sequential conformation of the substrate.     

Replicated high-density genetic maps of two great tit populations reveal fine-scale genomic departures from sex-equal recombination rates

Linking variation in quantitative traits to variation in the genome is an important, but challenging task in the study of life-history evolution. Linkage maps provide a valuable tool for the unravelling of such trait−gene associations. Moreover, they give insight into recombination landscapes and between-species karyotype evolution. Here we used genotype data, generated from a 10k single-nucleotide polymorphism (SNP) chip, of over 2000 individuals to produce high-density linkage maps of the great tit (Parus major), a passerine bird that serves as a model species for ecological and evolutionary questions. We created independent maps from two distinct populations: a captive F2-cross from The Netherlands (NL) and a wild population from the United Kingdom (UK). The two maps contained 6554 SNPs in 32 linkage groups, spanning 2010 cM and 1917 cM for the NL and UK populations, respectively, and were similar in size and marker order. Subtle levels of heterochiasmy within and between chromosomes were remarkably consistent between the populations, suggesting that the local departures from sex-equal recombination rates have evolved. This key and surprising result would have been impossible to detect if only one population was mapped. A comparison with zebra finch Taeniopygia guttata, chicken Gallus gallus and the green anole lizard Anolis carolinensis genomes provided further insight into the evolution of avian karyotypes.     

Inhibition of bongkrek acid and toxoflavin production in tempe bongkrek containing Pseudomonas cocovenenans

Tempe bongkrek was prepared from partially defatted coconut by fermentation with the mould Rhizopus oligosporus . The addition of 2% sodium chloride decreased but did not inhibit formation of bongkrek acid by Pseudomonas cocovenenans strain ITB in either coconut culture medium (CCM) or tempe bongkrek, while 2% sodium chloride or acidification of CCM to pH 4.5 with acetic acid inhibited formation of toxoflavin. Toxin formation by three strains of Ps. cocovenenans in tempe bongkrek was inhibited by the combination of 2% sodium chloride and reduction of pH to 4.5 with acetic acid. Mycelial growth of R. oligosporus was sometimes affected by toxin production by Ps. cocovenenans , but not by the addition of 2% sodium chloride and/or acidification of CCM to pH 4.5 with acetic acid.     

Vacuum Aspiration of the Uterus in Therapeutic Abortion

A prospective study of vacuum aspiration in 400 cases of therapeutic abortion is described showing that the procedure was quick, involving little blood loss in most cases, and that the complication rate was low. The routine use of this method in therapeutic abortion is recommended.