Crochelins: Siderophores with an Unprecedented Iron-Chelating Moiety from the Nitrogen-Fixing Bacterium Azotobacter chroococcum.

Microbes use siderophores to access essential iron resources in the environment. Over 500 siderophores are known, but they utilize a small set of common moieties to bind iron. Azotobacter chroococcum expresses iron-rich nitrogenases, with which it reduces N .

In Vitro Reconstitution of OxyA Enzymatic Activity Clarifies Late Steps in Vancomycin Biosynthesis.

Studies on the biosynthesis of glycopeptide antibiotics have provided many insights into the strategies that Nature employs to build architecturally strained molecules. A key structural feature of vancomycin, the founding member of this class, is a set of three aromatic cross-links that are introduced via yet unknown mechanisms. Previous reports have identified three cytochrome P450 enzymes involved in this process and demonstrated enzymatic activity for OxyB, which installs the first aromatic cross-link.

sp. ATCC 55076 harbours the largest actinomycete chromosome to date and the kistamicin biosynthetic gene cluster.

Glycopeptide antibiotics (GPAs) have served as potent clinical drugs and as an inspiration to chemists in various disciplines. Among known GPAs, complestatin, chloropeptin, and kistamicin are unique in that they contain an unusual indole-phenol crosslink. The mechanism of formation of this linkage is unknown, and to date, the biosynthetic gene cluster of only one GPA with an indole-phenol crosslink, that of complestatin, has been identified.

A structural phylogeny for understanding 2-oxoacid oxidoreductase function.

2-Oxoacid:ferredoxin oxidoreductases (OFORs) are essential enzymes in microbial one-carbon metabolism. They use thiamine pyrophosphate to reversibly cleave carbon-carbon bonds, generating low potential (∼-500mV) electrons. Crystallographic analysis of a recently discovered OFOR, an oxalate oxidoreductase (OOR), has provided a second view of OFOR architecture and active site composition.

One-carbon chemistry of oxalate oxidoreductase captured by X-ray crystallography.

Thiamine pyrophosphate (TPP)-dependent oxalate oxidoreductase (OOR) metabolizes oxalate, generating two molecules of CO2 and two low-potential electrons, thus providing both the carbon and reducing equivalents for operation of the Wood-Ljungdahl pathway of acetogenesis. Here we present structures of OOR in which two different reaction intermediate bound states have been trapped: the covalent adducts between TPP and oxalate and between TPP and CO2. These structures, along with the previously determined structure of substrate-free OOR, allow us to visualize how active site rearrangements can drive catalysis.

The Structure of an Oxalate Oxidoreductase Provides Insight into Microbial 2-Oxoacid Metabolism.

Thiamine pyrophosphate (TPP), a derivative of vitamin B1, is a versatile and ubiquitous cofactor. When coupled with [4Fe-4S] clusters in microbial 2-oxoacid:ferredoxin oxidoreductases (OFORs), TPP is involved in catalyzing low-potential redox reactions that are important for the synthesis of key metabolites and the reduction of N2, H(+), and CO2. We have determined the high-resolution (2.

μ(2)-Iodido-bis-{dimeth-yl[methyl-bis(quinolin-8-yl)silanyl-κN,Si,N']platinum(IV)} tetra-kis(penta-fluoro-phen-yl)borate dichloro-methane 0.66-solvate.

The title complex, [Pt(2)(CH(3))(4)(C(19)H(15)N(2)Si)(2)I][B(C(6)F(5))(4)]·0.66CH(2)Cl(2), resulted from an attempt to synthesize a stable five-coordinate platinum species via ligand abstraction of a six-coordinate platinum precursor. However, dimerization occurred after ligand abstraction, thereby yielding the compound described in this study.