Sulfolipid-1 Biosynthesis Restricts Mycobacterium tuberculosis Growth in Human Macrophages

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis, is a highly evolved human pathogen characterized by its formidable cell wall. Many unique lipids and glycolipids from the Mtb cell wall are thought to be virulence factors that mediate host-pathogen interactions. An intriguing example is Sulfolipid-1 (SL-1), a sulfated glycolipid that has been implicated in Mtb pathogenesis, although no direct role for SL-1 in virulence has been established. Previously, we described the biochemical activity of the sulfotransferase Stf0 that initiates SL-1 biosynthesis. Here we show that a stf0-deletion mutant exhibits augmented survival in human but not murine macrophages, suggesting that SL-1 negatively regulates the intracellular growth of Mtb in a species-specific manner. Furthermore, we demonstrate that SL-1 plays a role in mediating the susceptibility of Mtb to a human cationic antimicrobial peptide in vitro, despite being dispensable for maintaining overall cell envelope integrity. Thus, we hypothesize that the species-specific phenotype of the stf0 mutant is reflective of differences in antimycobacterial effector mechanisms of macrophages

A Solvent-Free Oxidation of Alcohols in an Organic Laboratory

An oxidation experiment for a first-year organic chemistry class is presented. This oxidation utilizes a solid mixture of CuSO4•5H2O and KMnO4 prepared by mortar and pestle. The oxidations take place under solvent-free conditions and near quantitative yields are obtained for the reactions. Thin-layer chromatography is used to monitor the progress of the reaction. This experiment provides for the simple oxidation of a secondary alcohol to a ketone using a relatively nontoxic oxidizing agent under solvent-free conditions

Mycobacterium tuberculosis Rv3406 is a type II alkyl sulfatase capable of sulfate scavenging.

The genome of Mycobacterium tuberculosis (Mtb) encodes nine putative sulfatases, none of which have a known function or substrate. Here, we characterize Mtb's single putative type II sulfatase, Rv3406, as a non-heme iron (II) and α-ketoglutarate-dependent dioxygenase that catalyzes the oxidation and subsequent cleavage of alkyl sulfate esters. Rv3406 was identified based on its homology to the alkyl sulfatase AtsK from Pseudomonas putida. Using an in vitro biochemical assay, we confirmed that Rv3406 is a sulfatase with a preference for alkyl sulfate substrates similar to those processed by AtsK. We determined the crystal structure of the apo Rv3406 sulfatase at 2.5 Å. The active site residues of Rv3406 and AtsK are essentially superimposable, suggesting that the two sulfatases share the same catalytic mechanism. Finally, we generated an Rv3406 mutant (Δrv3406) in Mtb to study the sulfatase's role in sulfate scavenging. The Δrv3406 strain did not replicate in minimal media with 2-ethyl hexyl sulfate as the sole sulfur source, in contrast to wild type Mtb or the complemented strain. We conclude that Rv3406 is an iron and α-ketoglutarate-dependent sulfate ester dioxygenase that has unique substrate specificity that is likely distinct from other Mtb sulfatases

Conditional Glycosylation in Eukaryotic Cells Using a Biocompatible Chemical Inducer of Dimerization

Conditional Glycosylation in Eukaryotic Cells Using a Biocompatible Chemical Inducer of Dimerizatio

The reaction catalyzed by Rv3406.

<p>The alpha carbon of an alkyl sulfate is oxidized by Rv3406 in the presence of α-ketoglutarate and spontaneously collapses to an aldehyde and sulfate, liberating CO₂ and succinate. The product formation was monitored using a coupled assay using LADH to reduce the aldehyde in a NADH dependent manner.</p

Protein alignment of alkyl sulfatase enzymes with taurine dioxygenase enzymes.

<p><b>Enzymes in bold have been biochemically characterized.</b> (A) Alignment of disordered loop 1 where the red boxes are indicating the taurine binding residues in taurine dioxygenases and the analogous amino acids in alkyl sulfatase enzymes. (B) Alignment of disordered loop 2 where the red box is indicating the conserved phenylalanine in taurine dioxygenases and the analogous tyrosine in alkyl sulfate enzymes.</p