Whole cell matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry and in situ structure analysis of streptocidins, a family of tyrocidine‐like cyclic peptides

Abstract

Streptocidins, a family of tyrocidine-like cyclic decapeptides, are an ideal demonstration object for the detection and in situ structure analysis of natural compounds directly in microbial cells using whole cell matrix-assisted laser desorption/ionization time-of-flight-mass spectrometry (MALDI-TOFMS), an emerging technique that can be used for rapid sensitive metabolic profiling of microorganisms. Five main members of the streptocidin family (A-E) were detected in Brevibacillus cells picked from agar plates and identified by in situ structure analysis with post-source decay MALDI-TOFMS. This efficient modern method allows the precise detection of metabolites within minutes without the need to isolate and purify the target compounds. The generated mass spectra are of similar quality to those obtained for the purified peptides. In addition, surface extracts were prepared by treating Brevibacillus cells with 70% acetonitrile in the presence of 0.1% trifluoroacetic acid and fractionated by high-resolution reversed-phase high-performance liquid chromatography (HPLC). In this way ten minor streptocidins were detected demonstrating the full biosynthetic variety of streptocidin production on the cellular level. The streptocidins differ from the well-known tyrocidines essentially in position 3 of the decapeptide chain by replacement of the aromatic amino acid (F/W) found in tyrocidines by L-leucine or L-valine.

In situ detection of the intermediates in the biosynthesis of surfactin, a lipoheptapeptide from Bacillus subtilis OKB 105, by whole‐cell cell matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry in combination with mutant analysis

“…In this study we investigated the biosynthesis of the lipoheptapeptide surfactin from B. subtilis OKB 105 and used whole‐cell MALDI‐TOFMS as an innovative technique for the detection of surfactin and biosynthetic intermediates in situ . In the last decade this innovative method has efficiently been applied for mass spectrometric fingerprinting30, 31 and metabolic profiling of microorganisms 7, 10, 27–29, 32–34. The mass spectrum in Fig.…”

“…MALDI‐TOF mass spectra were recorded using a Bruker Reflex MALDI‐TOF instrument equipped with a 337 nm nitrogen laser for desorption and ionization, as described previously 7, 10, 27–29 . α ‐Cyano‐4‐hydroxycinnamic acid (CCA) was used as matrix.…”

Consistency between chemotyping of single filaments of Planktothrix rubescens (cyanobacteria) by MALDI‐TOF and the peptide patterns of strains determined by HPLC‐MS

“…Matrix assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) has been applied successfully to characterize diverse bacterial strains and other organisms on the basis of their production of secondary metabolites or proteomic patterns 4–7. In previous studies it could be demonstrated that in cyanobacterial strains and samples, strain‐specific oligopeptide patterns can be quickly determined 8, 9.…”

Gas-Phase Sequencing of Cyclotides: Introduction of Selective Ring Opening at Dehydroalanine via Ion/Ion Reaction

“…In one example, the highly selective cleavage N-terminal to proline has been used to facilitate ring opening in the gas phase. 41,42 More recently, solution-phase conversion of arginine to ornithine was performed to selectively open cyclic peptides Cterminal to ornithine in the gas phase. 43,44 Finally, it has been shown that gold(I) cationization promotes ring opening Nterminal to oxidized lysine residues in the gas phase.…”