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11.
The role of the sugar moiety of glycopeptide antibiotics in chiral recognition was investigated with capillary electrophoresis. Two glycopeptide antibiotics, vancomycin and balhimycin, were employed as models since they possess the same aglycon and almost identical sugar moieties, however, with different attachment sites to the aglycon. The observed enantioselectivity of balhimycin for dansylated alpha-amino acids is 2.6 times higher than that of vancomycin. Blocking of the sugar amino group of balhimycin by N-carbamoylation reaction with KOCN led to a significantly decreased enantioselectivity compared to vancomycin, which remained almost the same upon carbamoylation. These results suggest a major role of the amino sugar together with its site of attachment to the aglycon. A dimerization-based mechanism is proposed to explain this phenomenon due to the fact that the dimerization properties of glycopeptides are similarly related to their glycosylation patterns; e.g., the dimerization constant of balhimycin is 78 times higher than that of vancomycin. Furthermore, the dimerization of glycopeptides promotes their affinity to carboxyl-containing ligands via cooperativity effects between the dimerization and the formation of glycopeptide-ligand complexes. The higher dimer stability probably leads to a more favorable conformation for chiral recognition. Thus, it is concluded that a weakened dimerization of N-carbamoylated balhimycin results in a decreased enantioselectivity. 相似文献
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Hornbogen T Riechers SP Prinz B Schultchen J Lang C Schmidt S Mügge C Turkanovic S Süssmuth RD Tauberger E Zocher R 《Chembiochem : a European journal of chemical biology》2007,8(9):1048-1054
A 51 kDa fusion protein incorporating the N-methyltransferase domain of the multienzyme enniatin synthetase from Fusarium scirpi was expressed in Saccharomyces cerevisiae. The protein was purified and found to bind S-adenosyl methionine (AdoMet) as demonstrated by cross-linking experiments with (14)C-methyl-AdoMet under UV irradiation. Cofactor binding at equilibrium conditions was followed by saturation transfer difference (STD) NMR spectroscopy, and the native conformation of the methyltransferase was assigned. STD NMR spectroscopy yielded significant signals for H(2) and H(8) of the adenine moiety, H(1') of D-ribose, and S-CH(3) group of AdoMet. Methyl group transfer catalyzed by the enzyme was demonstrated by using aminoacyl-N-acetylcysteamine thioesters (aminoacyl-SNACs) of L-Val, L-Ile, and L-Leu, which mimic the natural substrate amino acids of enniatin synthetase presented by the enzyme bound 4'-phosphopantetheine arm. In these experiments the enzyme was incubated in the presence of the corresponding aminoacyl-SNAC and (14)C-methyl-AdoMet for various lengths of time, for up to 30 min. N-[(14)C-Methyl]-aminoacyl-SNAC products were extracted with EtOAc and separated by TLC. Acid hydrolysis of the isolated labeled compounds yielded the corresponding N-[(14)C-methyl] amino acids. Further proof for the formation of N-(14)C-methyl-aminoacyl-SNACs came from MALDI-TOF mass spectrometry which yielded 23 212 Da for N-methyl-valyl-SNAC, accompanied by the expected postsource decay (PSD) pattern. Interestingly, L-Phe, which is not a substrate amino acid of enniatin synthetase, also proved to be a methyl group acceptor. D-Val was not accepted as a substrate; this indicates selectivity for the L isomer. 相似文献
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Sylvester Hoffmann Maik Damm Leonard Roth Prof. Dr. Roderich D. Süssmuth 《Chembiochem : a European journal of chemical biology》2023,24(13):e202300233
The fungal cyclodepsipeptides (CDPs) enniatin, beauvericin, bassianolide, and PF1022 consist of alternating N-methylated l -amino and d -hydroxy acids. They are synthesized by non-ribosomal peptide synthetases (NRPS). The amino acid and hydroxy acid substrates are activated by adenylation (A) domains. Although various A domains have been characterized thus giving insights into the mechanism of substrate conversion, little is known about the utilization of hydroxy acids in NRPSs. Therefore, we used homology modelling and molecular docking of the A1 domain of enniatin synthetase (EnSyn) to gain insights into the mechanism of hydroxy acid activation. We introduced point mutations into the active site and used a photometric assay to study the substrate activation. The results suggest that the hydroxy acid is selected by interaction with backbone carbonyls rather than by a specific side chain. These insights enhance the understanding of non-amino acid substrate activation and could contribute to the engineering of depsipeptide synthetases. 相似文献
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Rehan O’Grady Roderich Groß Anders Lyhne Christensen Marco Dorigo 《Autonomous Robots》2010,28(4):439-455
Robots are said to be capable of self-assembly when they can autonomously form physical connections with each other. By examining
different ways in which a system can use self-assembly (i.e., different strategies), we demonstrate and quantify the performance costs and benefits of (i) acting as a physically larger self-assembled entity,
(ii) letting the system choose when and if to self-assemble, (iii) coordinating the sensing and actuation of the connected
robots so that they respond to the environment as a single collective entity. Our analysis is primarily based on real world
experiments in a hill crossing task. The configuration of the hill is not known by the robots in advance—the hill can be present
or absent, and can vary in steepness and orientation. In some configurations, the robots can overcome the hill more quickly
by navigating individually, while other configurations require the robots to self-assemble to overcome the hill. We demonstrate
the applicability of our self-assembly strategies to two other tasks—hole crossing and robot rescue—for which we present further
proof-of-concept experiments with real robots. 相似文献
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This letter highlights a fundamental inconsistency in the formulation of the Gravitational search algorithm (GSA) (Rashedi et al., Inf Sci 2232?C48, 2009). GSA is said to be based on the law of gravity, that is, candidate solutions attract each other in the search space based on their relative distances and ??masses?? (qualities). We show that, contrary to what is claimed, GSA does not take the distances between solutions into account, and therefore cannot be considered to be based on the law of gravity. 相似文献
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Dennis Kerwat Stefan Grätz Dr. Julian Kretz Maria Seidel Maria Kunert Dr. John B. Weston Prof. Dr. Roderich D. Süssmuth 《ChemMedChem》2016,11(17):1899-1903
The peptide antibiotic albicidin, which is synthesized by the plant pathogenic bacterium, Xanthomonas albilineans, represents the most prominent member of a new class of antibacterial gyrase inhibitors. It shows remarkable antibacterial activities against Gram‐positive and Gram‐negative microorganisms. Its unique structure potentially represents a new lead structure for the development of an antibacterial drug. Here we report the synthesis of 14 albicidin derivatives with structural variations at the N‐terminus, primarily investigating the effects of variation of cinnamoyl, phenylpropanoyl, and benzoyl residues. Gyrase inhibition in vitro and determination of minimal inhibitory concentrations were assessed in parallel. Activities in a nanomolar range and the importance of N‐acylation were demonstrated. 相似文献