Discovery, production and purification of the Na+, K+ activated ATPase inhibitor, L-681,110 from the fermentation broth of Streptomyces sp. MA-5038.

The maximum yield for the production of L-681,110 by Streptomyces sp. MA-5038 (ATCC 31587) was observed after 5 days' incubation at 28 degrees C and pH about 8.3. L-681,110 was isolated from the fermentation broth by acetone extraction of the mycelia, absorption to Amberlite XAD-2 resin and two separations by thin-layer chromatography. The structure of L-681,110 was found to consist of a sixteen-membered lactone with a new type of substitution. The inhibition of ATPase, activity against Caenorhabditis elegans and stimulation of gamma-aminobutyric acid release indicate that L-681,110 possesses some characteristics of both oligomycin and avermectin. L-681,110 was also active against tapeworm and ticks in an in vivo assay.

Degradation of proteins in steady-state cultures of Escherichia coli.

The degradation of proteins in Escherichia coli was investigated in cells grown under steady-state conditions in a glucose-limited chemostat. During the first 24 h, approximately 25% of pulse-labeled proteins were degraded and after 72 h up to 58% of the proteins were broken down. To examine the stability of subcellular components steady-state cultures were labeled with an initial pulse of [14C]leucine, 24 h were allowed for turnover of these proteins, and the cells were then labeled with a short pulse of [3H]leucine. By this double-label protocol, the labile proteins were preferentially labeled with [H]leucine and had high 3H/14C ratios, while the more stable proteins had lower 3//14C ratios. The 3/-labeled proteins were degraded approximately five times as rapidly as the 14C-labeled proteins in exponentially growing cells. The relative stability of subcellular fractions was determined by comparing their 3H/14C ratios to the ratio of the cells at harvest. The soluble fraction contained the most labile proteins, while the ribosomal and membrane fractions were at least as stable as the average cell protein.