Peptidoglycan Cross-Linking in Glycopeptide-Resistant Actinomycetales

Oritavancin is a semisynthetic derivative of the glycopeptide antibiotic chloroeremomycin with activity against Gram-positive pathogens, including vancomycin-resistant staphylococci and enterococci. Compared to vancomycin, oritavancin is characterized by the presence of two additional residues, a hydrophobic 4=-chlorobiphenyl methyl moiety and a 4-epi-vancosamine substituent, which is also present in chloroeremomycin. Here, we show that oritavancin and its des-N-methylleucyl variant (

Section: Discussionmentioning

confidence: 99%

Structural Variations of the Cell Wall Precursor Lipid II and Their Influence on Binding and Activity of the Lipoglycopeptide Antibiotic Oritavancin

Münch

Engels

Müller

et al. 2015

“…The resistance profiles were therefore determined by the differences between the amino acid sequences of the VanR-VanS proteins present rather than by inherent differences in cell wall structure or biosynthesis between the strains. The activity of extracellular D,D-carboxypeptidases has been shown to alter the efficacy of glycopeptide antibi- (39), but the difference in the control by VanR-VanS is clearly the dominant factor differing between S. coelicolor and S. toyocaensis. The incomplete restoration of resistance to vancomycin in S. toyocaensis H2360 (⌬vanRSst vanRSsc) compared to the level of resistance of wild-type S. coelicolor could, however, suggest some contribution from differences in carboxypeptidase activity between strains, but this could also be due to a possible increase in the level of expression of staP from the A47934 cluster, which is known to have deleterious effects on growth (29).…”

Section: Discussionmentioning

confidence: 99%

In Vivo Characterization of the Activation and Interaction of the VanR-VanS Two-Component Regulatory System Controlling Glycopeptide Antibiotic Resistance in Two Related Streptomyces Species

Novotná

Kwun

Hong

2016

The VanR-VanS two-component system is responsible for inducing resistance to glycopeptide antibiotics in various bacteria. We have performed a comparative study of the VanR-VanS systems from two streptomyces strains, Streptomyces coelicolor and Streptomyces toyocaensis, to characterize how the two proteins cooperate to signal the presence of antibiotics and to define the functional nature of each protein in each strain background. The results indicate that the glycopeptide antibiotic inducer specificity is determined solely by the differences between the amino acid sequences of the VanR-VanS two-component systems present in each strain rather than by any inherent differences in general cell properties, including cell wall structure and biosynthesis. VanR of S. coelicolor (VanRsc) functioned with either sensor kinase partner, while VanR of S. toyocaensis (VanRst) functioned only with its cognate partner, S. toyocaensis VanS (VanSst). In contrast to VanRsc, which is known to be capable of phosphorylation by acetylphosphate, VanRst could not be activated in vivo independently of a VanS sensor kinase. A series of amino acid sequence modifications changing residues in the N-terminal receiver (REC) domain of VanRst to the corresponding residues present in VanRsc failed to create a protein capable of being activated by VanS of S. coelicolor (VanSsc), which suggests that interaction of the response regulator with its cognate sensor kinase may require a region more extended than the REC domain. A T69S amino acid substitution in the REC domain of VanRst produced a strain exhibiting weak constitutive resistance, indicating that this particular amino acid may play a key role for VanS-independent phosphorylation in the response regulator protein. Ever since the first clinical isolates of pathogenic strains of vancomycin-resistant enterococci (VRE) appeared in the late 1980s (1), the spread of vancomycin resistance through bacterial populations has been an acute public health issue, highlighted by the emergence of vancomycin-and methicillin-resistant Staphylococcus aureus (VRSA) strains in hospitals (2). Vancomycin inhibits cell wall biosynthesis by binding to the D-alanyl-D-alanine (D-Ala-D-Ala) terminus of lipid-attached peptidoglycan (PG) precursors on the outside of the cytoplasmic membrane. This interaction blocks the formation of mature PG, principally by denying transpeptidase enzymes access to their substrate and thereby preventing the formation of the peptide cross-links between polysaccharide strands that give the cell wall its rigidity (3). However, reprogramming of cell wall biosynthesis such that the stem pentapeptide of PG precursors terminates in D-alanyl-D-lactate (DAla-D-Lac) rather than in D-Ala-D-Ala can allow the cell to escape the action of vancomycin since the binding affinity of the drug for the new precursors is significantly lower than that for the original precursors (4-6). Reprogramming can be achieved via expression of dedicated glycopeptide antibiotic resistance gene clusters minimally consisting ...

“…An examination of the PG composition of a range of bacteria has revealed that LDTs are more prevalent than expected, especially among Actinomycetales, which show the following percentages of 3¡3 cross-links: 60 to 80% in mycobacteria, 38% in Corynebacterium jeikeium (41,44), 57% in S. coelicolor, and 49% (exponential phase) to 31% (stationary phase) in Nonomuraea sp. ATCC 39727 (45).…”

Section: Discussionmentioning

confidence: 99%

Relationship between Glycopeptide Production and Resistance in the Actinomycete Nonomuraea sp. ATCC 39727

Marcone

Binda

Carrano³

et al. 2014

dGlycopeptides and ␤-lactams inhibit bacterial peptidoglycan synthesis in Gram-positive bacteria; resistance to these antibiotics is studied intensively in enterococci and staphylococci because of their relevance to infectious disease. Much less is known about antibiotic resistance in glycopeptide-producing actinomycetes that are likely to represent the evolutionary source of resistance determinants found in bacterial pathogens. Nonomuraea sp. ATCC 39727, the producer of A40926 (the precursor for the semisynthetic dalbavancin), does not harbor the canonical vanHAX genes. Consequently, we investigated the role of the ␤-lactamsensitive D,D-peptidase/D,D-carboxypeptidase encoded by vanY n , the only van-like gene found in the A40926 biosynthetic gene cluster, in conferring immunity to the antibiotic in Nonomuraea sp. ATCC 39727. Taking advantage of the tools developed recently to genetically manipulate this uncommon actinomycete, we varied vanY n gene dosage and expressed vanH at A at X at from the teicoplanin producer Actinoplanes teichomyceticus in Nonomuraea sp. ATCC 39727. Knocking out vanY n , complementing a vanY n mutant, or duplicating vanY n had no effect on growth but influenced antibiotic resistance and, in the cases of complementation and duplication, antibiotic production. Nonomuraea sp. ATCC 39727 was found to be resistant to penicillins, but its glycopeptide resistance was diminished in the presence of penicillin G, which inhibits VanY n activity. The heterologous expression of vanH at A at X at increased A40926 resistance in Nonomuraea sp. ATCC 39727 but did not increase antibiotic production, indicating that the level of antibiotic production is not directly determined by the level of resistance. The vanY n -based self-resistance in Nonomuraea sp. ATCC 39727 resembles the glycopeptide resistance mechanism described recently in mutants of Enterococcus faecium selected in vitro for high-level resistance to glycopeptides and penicillins.