Bafilomycin B1

A new actinomycete strain NA4 was isolated from a deep-sea sediment collected from the South China Sea and showed promising antifungal activities against soilborne fungal pathogens. It was identified as Streptomyces cavourensis by morphological, physiological, and phylogenetic analyses based on its 16S rRNA gene sequence. The main antifungal components were isolated and identified from the fermentation culture as bafilomycins B1 and C1. These compounds exhibited significant antifungal activities and a broad antifungal spectrum. The results suggest that the Streptomyces cavourensis NA4 and bafilomycins B1 and C1 could be used as potential biocontrol agents for soilborne fungal diseases of plants.

A wave of beta cell apoptosis occurs around 2 weeks of age in rats and mice. We have previously reported that exposure in utero to bafilomycin, a plecomacrolide antibiotic that inhibits the vacuolar (v)ATPase enzyme and contaminates the human diet, delays this neonatal wave and accelerates diabetes in non-obese diabetic (NOD) mice. Here we exposed C57BL/6J mice in utero to bafilomycin and assessed the effects on islet morphology, apoptosis and activation of cell survival signaling in beta cells. The neonatal wave of beta cell apoptosis was associated with high expression and low phosphorylation of the pro-apoptotic Bcl-2 family protein Bad, whereas after weaning (3 weeks of age) Bad was down-regulated and beta cell apoptosis was low. In contrast, in bafilomycin-exposed mice the frequency of apoptotic beta cells and the expression of Bad remained high after weaning. Bafilomycin exposure also inactivated the insulin/IGF signaling pathway intermediate, FoxO1, and increased the insulin content in neonatal islets.

Rapid secretion relies on the occurrence of spike-like Ca2+ transients in active zones (Llinás et al., 1992; Yazejian et al., 2000; Dunant and Bloc, 2003). Presynaptic Ca2+ nanodomains are to be restricted both in time and in space as to assure rapid onset and termination of transmitter release (Llinás et al., 1992; Pozzan et al., 1994; Yazejian et al., 2000; Dunant and Bloc, 2003). A very fast Ca2+-buffering mechanism should allow Ca2+ rise above approximately 100 microM for less than approximately 250 micros and then rapid reduction of Ca2+ to subthreshold levels of release (Llinás et al., 1992; Pozzan et al., 1994; Yazejian et al., 2000; Dunant and Bloc, 2003). Swift Ca2+ clearance by vesicular Ca2+/H+ antiport as a low-affinity, high-capacity extrusion mechanism was postulated in the past (Pozzan et al., 1994; Dunant and Bloc, 2003). We demonstrated pH gradient (DeltapH)-dependent Ca2+ uptake by mammalian brain synaptic vesicles (Gonçalves et al.

The microbial macrolides bafilomycin A1, B, and concanamycin A from Streptomyces spp. are potent and specific inhibitors of V-ATPases. The question of the biosynthetic origin of the two uncommon "glycolate units" of each of the macrolide structures was addressed by feeding experiments with stereospecifically 13C-labeled precursors. Our studies clearly indicate that glycerol is a source for the methoxylated C2-units and determines the orientation of the incorporation. Products from the carboxylic acid pool or TCA cycle are ruled out as key precursors. The data suggest the action of a glycerol kinase and point to phosphoglycerate as an intermediate in their biosynthesis. However, glycerate itself is not accepted as a precursor. We present the likely biosynthetic pathway and show the value of stereospecifically labeled presursors as an important tool for biosynthetic investigations.