Characterization of two components of the 2-naphthoate monooxygenase system from Burkholderia sp. strain JT1500

2-Naphthoate monooxygenase, a two-protein system, encoded by the nmoA and nmoB genes, was heterologously overexpressed in Escherichia coli. The proteins used for functional characterization were purified to over 90% homogeneity by affinity chromatography. The oxidative component EnmoA (47.9 kDa) lacked substrate catalysis capability on its own, and the reductive component EnmoB (33.4 kDa) and its truncated derivate EnmoB(T) (25 kDa) possessed nearly identical independent flavin reductase activities, c. 130 micromol min(-1) mg(-1) of protein. The inframe fusioned protein EnmoB(T)A (65.2 kDa), containing NmoB(T) and NmoA peptides showed a stable 2-naphthoate monooxygenase activity of 1.2 micromol min(-1) mg(-1) of protein. This is the first report on the purification of a fused form of a two-component flavoprotein monooxygenase. In the specificity experiment, FAD and NADH were shown to be preferred cosubstrates for EnmoB and EnmoB(T). All these data suggest that NmoB(T)A is a two-component flavoprotein monooxygenase, consisting of an oxygenase and a reductase component. NmoA is a member of the class D flavoprotein monooxygenase, and NmoB is an independent NADH:Flavin oxidoreductase.     

Protecting mitochondria via inhibiting VDAC1 oligomerization alleviates ferroptosis in acetaminophen-induced acute liver injury

Cell Biology and Toxicology - Acetaminophen (APAP) overdose is a common cause of drug-induced liver injury (DILI). Ferroptosis has been recently implicated in APAP-induced liver injury (AILI)....     

Magnesium Lithospermate B Protects Neurons Against Amyloid β (1–42)-Induced Neurotoxicity Through the NF-κB Pathway

Neurochemical Research - Magnesium lithospermate B (MLB) is one of the major bioactive components of Radix Salviae miltiorrhizae, a Chinese traditional herbal medicine colloquially known as Dan...     

Changes in Patterns of Species Co‐occurrence across Two Tropical Cloud Forests Differing in Soil Nutrients and Air Temperature

Patterns of co‐occurrence of species are increasingly used to examine the contribution of biotic interactions to community assembly. We assessed patterns of co‐occurrence at four scales, in two types of tropical cloud forests in Hainan Island, China (tropical montane evergreen forests, TMEF and tropical dwarf forests, TDF) that varied significantly in soil nutrients and temperature. We tested if the patterns of co‐occurrence changed when we sorted species into classes by abundance and diameter at breast height (dbh). Co‐occurrence differed by forest type and with plot size, with significant species aggregation observed across larger plots in TDF and patterns of species segregation observed in smaller plots in TMEF. Analyses of differential abundance and dbh classes also showed that smaller plots in TMEF tend to have negative co‐occurrence patterns, but larger plots in TDF tend to show patterns of aggregation, suggesting competitive and facilitative interactions. This underscores the scale‐dependence of the processes contributing to community assembly. Furthermore, it is consistent with predictions of the stress gradient hypothesis that facilitation will be most important in biological systems subject to abiotic stress, while competition will be more important in less abiotically stressful habitats. Our results clearly demonstrate that these two types of tropical cloud forest exhibit different co‐occurrence patterns, and that these patterns are scale‐dependent, though independent of plant abundance and size class.