2-Aminobenzothiazoles Inhibit Virulence Gene Expression and Block Polymyxin Resistance in Salmonella enterica.

One promising strategy to combat antibiotic-resistant bacteria is to develop compounds that block bacterial defenses against antibacterial conditions produced by the innate immune system. Salmonella enterica, which causes food-borne gastroenteritis and typhoid fever, requires histidine kinases (HKs) to resist innate immune defenses such as cationic antimicrobial peptides (CAMPs). Herein, we report that 2-aminobenzothiazoles block histidine kinase-dependent phenotypes in Salmonella enterica serotype Typhimurium.

A Call for Better Integrated Policies to Accelerate the Fertility Decline in Sub-Saharan Africa.

To accelerate their demographic transition, sub-Saharan African (SSA) countries must trigger significant and rapid fertility declines. These fertility declines will open a demographic window of opportunity and enable countries to capture a first demographic dividend. Despite some successes, many programs aimed at decreasing fertility in SSA have yielded disappointing results.

Closed fumarase C active-site structures reveal SS Loop residue contribution in catalysis.

Fumarase C (FumC) catalyzes the reversible conversion of fumarate to S-malate. Previous structural investigations within the superfamily have reported a dynamic structural segment, termed the SS Loop. To date, active-site asymmetry has raised the question of how SS Loop placement affects participation of key residues during the reaction.

The structure of DcrB, a lipoprotein from Salmonella enterica, reveals flexibility in the N-terminal segment of the Mog1p/PsbP-like fold.

DcrB is an 18 kDa lipoprotein that contains a single domain of unknown function. DcrB is found within Enterobacteriaceae, a family of Gram-negative bacteria which includes pathogens that can cause food-borne illness and hospital-acquired infections. In Salmonella enterica serovar Typhimurium, DcrB is up-regulated by conditions that promote the production of known virulence factors.

UDP-galactopyranose mutase in nematodes.

Nematodes represent a diverse phylum of both free living and parasitic species. While the species Caenorhabditis elegans is a valuable model organism, parasitic nematodes or helminths pose a serious threat to human health. Indeed, helminths cause many neglected tropical diseases that afflict humans.

Conflicting roles for a cell surface modification in Salmonella.

Chemical modifications of components of the bacterial cell envelope can enhance resistance to antimicrobial agents. Why then are such modifications produced only under specific conditions? Here, we address this question by examining the role of regulated variations in O-antigen length in the lipopolysaccharide (LPS), a glycolipid that forms most of the outer leaflet of the outer membrane in Gram-negative bacteria. We determined that activation of the PmrA/PmrB two-component system, which is the major regulator of LPS alterations in Salmonella enterica serovar Typhimurium, impaired growth of Salmonella in bile.

A processive carbohydrate polymerase that mediates bifunctional catalysis using a single active site.

Even in the absence of a template, glycosyltransferases can catalyze the synthesis of carbohydrate polymers of specific sequence. The paradigm has been that one enzyme catalyzes the formation of one type of glycosidic linkage, yet certain glycosyltransferases generate polysaccharide sequences composed of two distinct linkage types. In principle, bifunctional glycosyltransferases can possess separate active sites for each catalytic activity or one active site with dual activities.

A tethering mechanism for length control in a processive carbohydrate polymerization.

Carbohydrate polymers are the most abundant organic substances on earth. Their degrees of polymerization range from tens to thousands of units, yet polymerases generate the relevant lengths without the aid of a template. To gain insight into template-independent length control, we investigated how the mycobacterial galactofuranosyl-transferase GlfT2 mediates formation of the galactan, a polymer of galactofuranose residues that is an integral part of the cell wall.

Inhibitors of UDP-galactopyranose mutase thwart mycobacterial growth.

Galactofuranose (Galf) residues are fundamental components of the cell wall of mycobacteria. A key enzyme, UDP-galactopyranose mutase (UGM), that participates in Galf incorporation mediates isomerization of UDP-Galf from UDP-galactopyranose (UDP-Galp). UGM is of special interest as a therapeutic target because the gene encoding it is essential for mycobacterial viability and there is no comparable enzyme in humans.

Chemical probes of UDP-galactopyranose mutase.

Many pathogenic prokaryotes and eukaryotes possess the machinery required to assemble galactofuranose (Galf)-containing glycoconjugates; these glycoconjugates can be critical for virulence or viability. Accordingly, compounds that block Galf incorporation may serve as therapeutic leads or as probes of the function of Galf-containing glycoconjugates. The enzyme UDP-galactopyranose mutase (UGM) is the only known generator of UDP-galactofuranose, the precursor to Galf residues.

Methyl scanning: total synthesis of demethylasterriquinone B1 and derivatives for identification of sites of interaction with and isolation of its receptor(s).

The principle of methyl scanning is proposed for determination of the sites of interaction between biologically active small molecules and their macromolecular target(s). It involves the systematic preparation of a family of methylated derivatives of a compound and their biological testing. As a functional assay, the method can identify the regions of a molecule that are important (and unimportant) for biological activity against even unknown targets, and thus provides an excellent complement to structural biology.