Total structure of the highly modified peptide antibiotic components of thiopeptin.

Abstract

On the basis of 'H and 13C NMR evidence, the structures of two series of the highly modified sulfur-containing peptide antibiotic thiopeptin were elucidated.The thiopeptins produced by Streptomyces tateyamensis belong to a group of highly modified sulfur containing peptide antibiotics'), the structures of several having only recently been determined by X-ray crystallography or physical methods=`'). They inhibit primarily Gram-positive bacteria'> and exhibit no significant differences in their inhibition of protein synthesis in cell-free Escherichia coli10). Thiopeptin B, the major component is valuable as a feed-additive because of its marked growth promoting action in swine and chickens11) and was recently shown to be effective as a lactic-acidosis preventive in sheep and cattle12).Thiopeptin B and four minor components A,, A, A> and A, were characterized by MIYAIRI et al.9.13) and shown primarily by acid hydrolysis experiments") to be closely related to the antibiotic thiostrepton, whose structure, with the exception of the side chain, was determined by X-ray crystallography by ANDERSON and coworkers-2). TORi et al.,3) from a "C NMR study of the antibiotic, proposed a sequence consisting of two dehydroalanine (Deala) residues for the side chain which was subsequently confirmed by our own 'H NMR study at 300 MHz (see preceding paper). Of the spectroscopic techniques available to us it soon became apparent that only 'H and 1>C NMR spectroscopy were to be potentially useful in the structural elucidation of the thiopeptins. The molecules were not sufficiently volatile to yield a molecular ion even under field-desorption conditions and only a fragment involving the dihydroquinoline moiety and adjacent peptide was identifiable (see below). Moreover, despite the fact that some of the a components were obtained in crystalline form, they were found not to be suitable for X-ray crystallography. A strategy, involving 'H NMR comparison with thiostrepton, was therefore adopted in order to delineate their structural differences. Pertinent details of confirmatory 1>C NMR evidence are also discussed") whereas a full discussion of the 11C NMR assignments is the subject of a companion paper. Results and DiscussionThiopeptin components were separated by silica gel chromatography similar to that previously described') and found to be homogeneous by TLC. 'H NMR analysis of the components from various batches however, indicated a two compound system in the majority of cases which was confirmed by HPLC. Consistent differences in the 'H NMR spectra allowed them to be grouped into two distinct series arbitrarily designated by the subscripts a and b and some of their physical and chemical properties are summarized in Table 1. In some batches all components from the a series and only Al,, from the b

Metabolic initiation of differentiation and secondary metabolism by Streptomyces griseus: significance of the stringent response (ppGpp) and GTP content in relation to A factor

“…In B. subtilis, relaxed (reiC) mutants, lacking ribosomal protein BS-L11, have been previously recovered as thiostrepton-resistant isolates (33,34). In the present study, thiopeptin, an analog of thiostrepton (14), was used to isolate drug-resistant mutants of S. griselus. Among thiopeptin-resistant isolates, 25 strains selected randomly were tested for their ability to accumulate ppGpp during nutritional shift down, i.e., Casamino Acids deprivation.…”

“…A factor was assayed by using an S. griseus mutant (number 14) defective in A-factor synthesis. A factor produced in a medium was always extracted with an equal volume of chloroform, and the extract was then assayed by the method of Hara and Beppu (11) with slight modification.…”

Ribosomally synthesized and post-translationally modified peptide natural products: overview and recommendations for a universal nomenclature

“…214,219 Series a thiopeptides, exemplified by certain thiopeptins, present the core heterocycle as a fully saturated piperidine. 219,220 Series b is classically represented by thiostrepton A and its dehydropiperidine ring. 221 Series c , thus far, is comprised of a single entry, Sch 40832, in which the core nitrogen heterocycle is contained within an imidazopiperidine.…”

Pharmacologically Active Sulfur-Containing Compounds

“…Siomycins (34-37) isolated from Streptomyces sioyaensis and active against Gram-positive bacteria and mycobacteria [28,29] represent another group of compounds. The thiopeptins (38)(39)(40)(41)(42)(43)(44)(45) [30,31]. Sch 18640, isolated from Micromonospora arborensis [32], may serve as a representative of compounds produced by a microorganism different from Streptomyces.…”