The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform

Wolfgang Wohlleben - One of the best experts on this subject based on the ideXlab platform.

  • proteomic approach to reveal the regulatory function of aconitase acna in oxidative stress response in the antibiotic producer Streptomyces Viridochromogenes tu494
    PLOS ONE, 2014
    Co-Authors: Ewelina Michta, Wolfgang Wohlleben, Kai Blin, Wei Ding, Shaochun Zhu, Hongqiang Ruan, Rui Wang, Yvonne Mast
    Abstract:

    The aconitase AcnA from the phosphinothricin tripeptide producing strain Streptomyces Viridochromogenes Tu494 is a bifunctional protein: under iron-sufficiency conditions AcnA functions as an enzyme of the tricarboxylic acid cycle, whereas under iron depletion it is a regulator of iron metabolism and oxidative stress response. As a member of the family of iron regulatory proteins (IRP), AcnA binds to characteristic iron responsive element (IRE) binding motifs and post-transcriptionally controls the expression of respective target genes. A S. Viridochromogenes aconitase mutant (MacnA) has previously been shown to be highly sensitive to oxidative stress. In the present paper, we performed a comparative proteomic approach with the S. Viridochromogenes wild-type and the MacnA mutant strain under oxidative stress conditions to identify proteins that are under control of the AcnA-mediated regulation. We identified up to 90 differentially expressed proteins in both strains. In silico analysis of the corresponding gene sequences revealed the presence of IRE motifs on some of the respective target mRNAs. From this proteome study we have in vivo evidences for a direct AcnA-mediated regulation upon oxidative stress.

  • The bifunctional role of aconitase in Streptomyces Viridochromogenes Tü494
    Environmental microbiology, 2012
    Co-Authors: Ewelina Michta, Wolfgang Wohlleben, Eva Schinko, Klaus Schad, Kai Blin, Regina Ort-winklbauer, Marc Röttig, Oliver Kohlbacher, Yvonne Mast
    Abstract:

    Summary In many organisms, aconitases have dual functions; they serve as enzymes in the tricarboxylic acid cycle and as regulators of iron metabolism. In this study we defined the role of the aconitase AcnA in Streptomyces Viridochromogenes Tu494, the producer of the herbicide phosphinothricyl-alanyl-alanine, also known as phosphinothricin tripeptide or bialaphos. A mutant in which the aconitase gene acnA was disrupted showed severe defects in morphology and physiology, as it was unable to form any aerial mycelium, spores nor phosphinothricin tripeptide. AcnA belongs to the iron regulatory proteins (IRPs). In addition to its catalytic function, AcnA plays a regulatory role by binding to iron responsive elements (IREs) located on the untranslated region of certain mRNAs. A mutation preventing the formation of the [4Fe-4S] cluster of AcnA eliminated its catalytic activity, but did not inhibit RNA-binding ability. In silico analysis of the S. Viridochromogenes genome revealed several IRE-like structures. One structure is located upstream of recA, which is involved in the bacterial SOS response, and another one was identified upstream of ftsZ, which is required for the onset of sporulation in streptomycetes. The functionality of different IRE structures was proven with gel shift assays and specific IRE consensus sequences were defined. Furthermore, RecA was shown to be upregulated on post-transcriptional level under oxidative stress conditions in the wild-type strain but not in the acnA mutant, suggesting a regulatory role of AcnA in oxidative stress response.

  • Three Thioesterases Are Involved in the Biosynthesis of Phosphinothricin Tripeptide in Streptomyces Viridochromogenes Tü494
    Antimicrobial agents and chemotherapy, 2008
    Co-Authors: Sema Eys, Wolfgang Wohlleben, D. Schwartz, Eva Schinko
    Abstract:

    Phosphinothricin tripeptide (PTT) is a peptide antibiotic produced by Streptomyces Viridochromogenes Tu494, and it is synthesized by nonribosomal peptide synthetases. The PTT biosynthetic gene cluster contains three peptide synthetase genes: phsA, phsB, and phsC. Each of these peptide synthetases comprises only one module. In neither PhsB nor PhsC is a typical C-terminal thioesterase domain present. In contrast, a single thioesterase GXSXG motif has been identified in the N terminus of the first peptide synthetase, PhsA. In addition, two external thioesterase genes, theA and theB, are located within the PTT biosynthetic gene cluster. To analyze the thioesterase function as well as the assembly of the peptide synthetases within PTT biosynthesis, several mutants were generated and analyzed. A phsA deletion mutant (MphsA) was complemented with two different phsA constructs that were carrying mutations in the thioesterase motif. In one construct, the thioesterase motif comprising 45 amino acids of phsA were deleted. In the second construct, the conserved serine residue of the GXSXG motif was replaced by an alanine. In both cases, the complementation of MphsA did not restore PTT biosynthesis, revealing that the thioesterase motif in the N terminus of PhsA is required for PTT production. In contrast, TheA and TheB might have editing functions, as an interruption of the theA and theB genes led to reduced PTT production, whereas an overexpression of both genes in the wild type enhanced the PTT yield. The presence of an active single thioesterase motif in the N terminus of PhsA points to a novel mechanism of product release.

  • Phosphinothricin Tripeptide Synthetases in Streptomyces Viridochromogenes Tü494
    Antimicrobial agents and chemotherapy, 2005
    Co-Authors: D. Schwartz, Nicolas Grammel, Ullrich Keller, Eva Heinzelmann, Wolfgang Wohlleben
    Abstract:

    The tripeptide backbone of phosphinothricin (PT) tripeptide (PTT), a compound with herbicidal activity from Streptomyces Viridochromogenes, is assembled by three stand-alone peptide synthetase modules. The enzyme PhsA (66 kDa) recruits the PT-precursor N-acetyl-demethylphosphinothricin (N-Ac-DMPT), whereas the two alanine residues of PTT are assembled by the enzymes PhsB and PhsC (129 and 119 kDa, respectively). During or after assembly, the N-Ac-DMPT residue in the peptide is converted to PT by methylation and deacetylation. Both phsB and phsC appear to be cotranscribed together with two other genes from a single promoter and they are located at a distance of 20 kb from the gene phsA, encoding PhsA, in the PTT biosynthesis gene cluster of S. Viridochromogenes. PhsB and PhsC represent single nonribosomal peptide synthetase elongation modules lacking a thioesterase domain. Gene inactivations, genetic complementations, determinations of substrate specificity of the heterologously produced proteins, and comparison of PhsC sequence with the amino terminus of the alanine-activating nonribosomal peptide synthetase PTTSII from S. Viridochromogenes confirmed the role of the two genes in the bialanylation of Ac-DMPT. The lack of an integral thioesterase domain in the PTT assembly system points to product release possibly involving two type II thioesterase genes (the1 and the2) located in the PTT gene cluster alone or in conjunction with an as yet unknown mechanism of product release.

  • Biosynthetic Gene Cluster of the Herbicide Phosphinothricin Tripeptide from Streptomyces Viridochromogenes Tü494
    Applied and environmental microbiology, 2004
    Co-Authors: D. Schwartz, Eva Heinzelmann, Susanne Berger, Konstanze Muschko, Kathrin Welzel, Wolfgang Wohlleben
    Abstract:

    The antibiotic phosphinothricin tripeptide (PTT) consists of two molecules of l-alanine and one molecule of the unusual amino acid phosphinothricin (PT) which are nonribosomally combined. The bioactive compound PT has bactericidal, fungicidal, and herbicidal properties and possesses a C—P—C bond, which is very rare in natural compounds. Previously uncharacterized flanking and middle regions of the PTT biosynthetic gene cluster from Streptomyces Viridochromogenes Tu494 were isolated and sequenced. The boundaries of the gene cluster were identified by gene inactivation studies. Sequence analysis and homology searches led to the completion of the gene cluster, which consists of 24 genes. Four of these were identified as undescribed genes coding for proteins that are probably involved in uncharacterized early steps of antibiotic biosynthesis or in providing precursors of PTT biosynthesis (phosphoenolpyruvate, acetyl-coenzyme A, or l-alanine). The involvement of the genes orfM and trs and of the regulatory gene prpA in PTT biosynthesis was analyzed by gene inactivation and overexpression, respectively. Insight into the regulation of PTT was gained by determining the transcriptional start sites of the pmi and prpA genes. A previously undescribed regulatory gene involved in morphological differentiation in streptomycetes was identified outside of the left boundary of the PTT biosynthetic gene cluster.

D. Schwartz - One of the best experts on this subject based on the ideXlab platform.

  • Three Thioesterases Are Involved in the Biosynthesis of Phosphinothricin Tripeptide in Streptomyces Viridochromogenes Tü494
    Antimicrobial agents and chemotherapy, 2008
    Co-Authors: Sema Eys, Wolfgang Wohlleben, D. Schwartz, Eva Schinko
    Abstract:

    Phosphinothricin tripeptide (PTT) is a peptide antibiotic produced by Streptomyces Viridochromogenes Tu494, and it is synthesized by nonribosomal peptide synthetases. The PTT biosynthetic gene cluster contains three peptide synthetase genes: phsA, phsB, and phsC. Each of these peptide synthetases comprises only one module. In neither PhsB nor PhsC is a typical C-terminal thioesterase domain present. In contrast, a single thioesterase GXSXG motif has been identified in the N terminus of the first peptide synthetase, PhsA. In addition, two external thioesterase genes, theA and theB, are located within the PTT biosynthetic gene cluster. To analyze the thioesterase function as well as the assembly of the peptide synthetases within PTT biosynthesis, several mutants were generated and analyzed. A phsA deletion mutant (MphsA) was complemented with two different phsA constructs that were carrying mutations in the thioesterase motif. In one construct, the thioesterase motif comprising 45 amino acids of phsA were deleted. In the second construct, the conserved serine residue of the GXSXG motif was replaced by an alanine. In both cases, the complementation of MphsA did not restore PTT biosynthesis, revealing that the thioesterase motif in the N terminus of PhsA is required for PTT production. In contrast, TheA and TheB might have editing functions, as an interruption of the theA and theB genes led to reduced PTT production, whereas an overexpression of both genes in the wild type enhanced the PTT yield. The presence of an active single thioesterase motif in the N terminus of PhsA points to a novel mechanism of product release.

  • Phosphinothricin Tripeptide Synthetases in Streptomyces Viridochromogenes Tü494
    Antimicrobial agents and chemotherapy, 2005
    Co-Authors: D. Schwartz, Nicolas Grammel, Ullrich Keller, Eva Heinzelmann, Wolfgang Wohlleben
    Abstract:

    The tripeptide backbone of phosphinothricin (PT) tripeptide (PTT), a compound with herbicidal activity from Streptomyces Viridochromogenes, is assembled by three stand-alone peptide synthetase modules. The enzyme PhsA (66 kDa) recruits the PT-precursor N-acetyl-demethylphosphinothricin (N-Ac-DMPT), whereas the two alanine residues of PTT are assembled by the enzymes PhsB and PhsC (129 and 119 kDa, respectively). During or after assembly, the N-Ac-DMPT residue in the peptide is converted to PT by methylation and deacetylation. Both phsB and phsC appear to be cotranscribed together with two other genes from a single promoter and they are located at a distance of 20 kb from the gene phsA, encoding PhsA, in the PTT biosynthesis gene cluster of S. Viridochromogenes. PhsB and PhsC represent single nonribosomal peptide synthetase elongation modules lacking a thioesterase domain. Gene inactivations, genetic complementations, determinations of substrate specificity of the heterologously produced proteins, and comparison of PhsC sequence with the amino terminus of the alanine-activating nonribosomal peptide synthetase PTTSII from S. Viridochromogenes confirmed the role of the two genes in the bialanylation of Ac-DMPT. The lack of an integral thioesterase domain in the PTT assembly system points to product release possibly involving two type II thioesterase genes (the1 and the2) located in the PTT gene cluster alone or in conjunction with an as yet unknown mechanism of product release.

  • Biosynthetic Gene Cluster of the Herbicide Phosphinothricin Tripeptide from Streptomyces Viridochromogenes Tü494
    Applied and environmental microbiology, 2004
    Co-Authors: D. Schwartz, Eva Heinzelmann, Susanne Berger, Konstanze Muschko, Kathrin Welzel, Wolfgang Wohlleben
    Abstract:

    The antibiotic phosphinothricin tripeptide (PTT) consists of two molecules of l-alanine and one molecule of the unusual amino acid phosphinothricin (PT) which are nonribosomally combined. The bioactive compound PT has bactericidal, fungicidal, and herbicidal properties and possesses a C—P—C bond, which is very rare in natural compounds. Previously uncharacterized flanking and middle regions of the PTT biosynthetic gene cluster from Streptomyces Viridochromogenes Tu494 were isolated and sequenced. The boundaries of the gene cluster were identified by gene inactivation studies. Sequence analysis and homology searches led to the completion of the gene cluster, which consists of 24 genes. Four of these were identified as undescribed genes coding for proteins that are probably involved in uncharacterized early steps of antibiotic biosynthesis or in providing precursors of PTT biosynthesis (phosphoenolpyruvate, acetyl-coenzyme A, or l-alanine). The involvement of the genes orfM and trs and of the regulatory gene prpA in PTT biosynthesis was analyzed by gene inactivation and overexpression, respectively. Insight into the regulation of PTT was gained by determining the transcriptional start sites of the pmi and prpA genes. A previously undescribed regulatory gene involved in morphological differentiation in streptomycetes was identified outside of the left boundary of the PTT biosynthetic gene cluster.

  • Tricarboxylic acid cycle aconitase activity during the life cycle of Streptomyces Viridochromogenes Tü494
    Archives of microbiology, 2002
    Co-Authors: Konstanze Muschko, Wolfgang Wohlleben, G. Kienzlen, Hans-peter Fiedler, D. Schwartz
    Abstract:

    Previously, it was shown that inactivation of the tricarboxylic acid cycle aconitase gene acnA impairs the morphological and physiological differentiation of Streptomyces Viridochromogenes Tu494, which produces the herbicide phosphinothricin tripeptide (PTT). In order to further characterize the role of the aconitase in the Streptomyces life cycle, aconitase activity was analyzed during growth of S. Viridochromogenes in liquid culture. Two prominent maxima were measured in cell-free crude extracts. The first maximum was found at an early stage of growth, which is correlated with a decrease in pH when rapid glucose consumption is initiated. The second, lower maximum was detected at the beginning of the expression of the PTT-specific biosynthetic gene phsA, implying the onset of secondary metabolism. These results were confirmed by examining transcription of the acnA promoter in time-course experiments. The highest transcription rate was found during the early growth phases. In order to identify putative regulatory mechanisms, the transcriptional start site of the acnA transcript and subsequently the promoter were identified. Several putative, regulatory protein binding sites (e.g. regulators of oxygen stress or iron metabolism) were detected in the promoter region of acnA, which suggested complex regulation of acnA.

  • The phosphinomethylmalate isomerase gene pmi, encoding an aconitase-like enzyme, is involved in the synthesis of phosphinothricin tripeptide in Streptomyces Viridochromogenes.
    Applied and environmental microbiology, 2001
    Co-Authors: Eva Heinzelmann, Wolfgang Wohlleben, S. Kaspar, G. Kienzlen, J. Recktenwald, D. Schwartz
    Abstract:

    The structurally identical antibiotics phosphinothricin tripeptide (PTT) and bialaphos are produced by Streptomyces Viridochromogenes and by Streptomyces hygroscopicus (4, 18), respectively. They consist of two molecules, l-alanine and one molecule of the unusual amino acid phosphinothricin (PT). A biosynthetic pathway for bialaphos, consisting of at least 13 steps, was postulated following analysis of nonproducing S. hygroscopicus mutants (summarized in reference 35). Several enzymes were purified, and various genes of the PTT biosynthetic gene cluster were mapped in S. hygroscopicus (35), as well as in S. Viridochromogenes (1, 12, 28, 32). It was shown that the respective genes and enzymes were highly similar (up to 80%) on the DNA and amino acid levels (29, 39, 40). As the genetic organizations of the two clusters are basically identical, it has been concluded that the biosynthesis in both producing strains proceeds in the same way. The biosynthetic steps 6, 7, and 8 were found to be similar to the citrate synthase, aconitase, and isocitrate dehydrogenase reactions of the tricarboxylic acid (TCA) cycle, respectively (Fig. ​(Fig.1).1). In contrast to the step 6 reaction, for which a specific PTT biosynthetic gene and protein were identified (15), the subsequent steps, especially the isomerization of phosphinomethylmalate in step 7, were speculated to be catalyzed by the enzymes of the primary metabolism (35). Three facts supported this. First, inhibition of aconitase resulted in a PTT-negative phenotype; second, no mutants blocked in these steps could be generated by nonspecific mutagenesis; and third, biotransformations using crude cell extracts from Streptomyces lividans or Brevibacterium lactofermentum were possible (35). FIG. 1 Comparison of selected reactions of PTT biosynthesis and the TCA cycle. The isomerizations of citrate and of phosphinomethylmalic acid are marked by boxes. The isolation and characterization of a PTT biosynthesis-specific aconitase-like gene in S. Viridochromogenes, described in this paper, casts doubt on this hypothesis.

Gerald Pattenden - One of the best experts on this subject based on the ideXlab platform.

Andreas Bechthold - One of the best experts on this subject based on the ideXlab platform.

  • Structure and function of the antibiotic resistance-mediating methyltransferase AviRb from Streptomyces Viridochromogenes
    Journal of molecular biology, 2005
    Co-Authors: Tanja G. Mosbacher, Andreas Bechthold, Georg E. Schulz
    Abstract:

    The emergence of antibiotic-resistant bacterial strains is a widespread problem in medical practice and drug design, and each case requires the elucidation of the underlying mechanism. AviRb from Streptomyces Viridochromogenes methylates the 2′-O atom of U2479 of the 23 S ribosomal RNA in Gram-positive bacteria and thus mediates resistance to the oligosaccharide (orthosomycin) antibiotic avilamycin. The structure of AviRb with and without bound cofactor S- adenosyl- l -methionine (AdoMet) was determined, showing that it is a homodimer belonging to the SpoU family within the SPOUT class of methyltransferases. The relationships within this class were analyzed in detail and, in addition, a novel fourth SpoU sequence fingerprint is proposed. Each subunit of AviRb consists of two domains. The N-terminal domain, being related to the ribosomal proteins L30 and L7Ae, is likely to bind RNA. The C-terminal domain is related to all SPOUT methyltransferases, and is responsible for AdoMet-binding, catalysis and dimerization. The cofactor binds at the characteristic knot of the polypeptide in an unusually bent conformation. The transferred methyl group points to a broad cleft formed with the L30-type domain of the other subunit. Measurements of mutant activity revealed four important residues responsible for catalysis and allowed the modeling of a complex between AviRb and the RNA target. The model includes a specificity pocket for uracil but does not contain a base for deprotonating the 2′-O atom of U2479 on methylation.

  • Novel Avilamycin Derivatives with Improved Polarity Generated by Targeted Gene Disruption
    Chemistry & biology, 2004
    Co-Authors: Gabriele Weitnauer, Gerd Hauser, Carsten Hofmann, Ulrike Linder, Raija Boll, Klaus Pelz, Steffen J. Glaser, Andreas Bechthold
    Abstract:

    The oligosaccharide antibiotics avilamycin A and C are produced by Streptomyces Viridochromogenes Tu57. Both consist of a heptasaccharide chain, which is attached to a polyketide-derived dichloroisoeverninic acid moiety. They show excellent antibiotic activity against Gram-positive bacteria. Both molecules are modified by O-methylation at different positions, which contributes to poor water solubility and difficulties in galenical drug development. In order to generate novel avilamycin derivatives with improved polarity and improved pharmacokinetic properties, we generated a series of mutants with one, two, or three mutated methyltransferase genes. Based on the structure of the novel avilamycin derivatives, the exact function of three methyltransferases, AviG2, AviG5, and AviG6, involved in avilamycin biosynthesis could be assigned.

  • Crystal structure of the avilamycin resistance-conferring methyltransferase AviRa from Streptomyces Viridochromogenes.
    Journal of molecular biology, 2003
    Co-Authors: Tanja G. Mosbacher, Andreas Bechthold, Georg E. Schulz
    Abstract:

    The emergence of antibiotic-resistant bacterial strains is a widespread problem in contemporary medical practice and drug design. It is therefore important to elucidate the underlying mechanism in each case. The methyltransferase AviRa from Streptomyces Viridochromogenes mediates resistance to the antibiotic avilamycin, which is closely related to evernimicin, an oligosaccharide antibiotic that has been used in medical studies. The structure of AviRa was determined by X-ray diffraction at 1.5A resolution. Phases were obtained from one selenomethionine residue introduced by site-directed mutagenesis. The chain-fold is similar to that of most methyltransferases, although AviRa contains two additional helices as a specific feature. A putative-binding site for the cofactor S-adenosyl-L-methionine was derived from homologous structures. It agrees with the conserved pattern of interacting amino acid residues. AviRa methylates a specific guanine base within the peptidyltransferase loop of the 23S ribosomal RNA. Guided by the target, the enzyme was docked to the cognate ribosomal surface, where it fit well into a deep cleft without contacting any ribosomal protein. The two additional alpha-helices of AviRa filled a depression in the surface. Since the transferred methyl group of the cofactor is in a pocket beneath the enzyme surface, the targeted guanine base has to flip out for methylation.

  • analysis of a c methyltransferase gene avig1 involved in avilamycin biosynthesis in Streptomyces Viridochromogenes tu57 and complementation of a saccharopolyspora erythraea erybiii mutant by avig1
    Microbiology, 2002
    Co-Authors: Gabriele Weitnauer, Sabine Gaisser, Laurenz Kellenberger, Peter F Leadlay, Andreas Bechthold
    Abstract:

    Streptomyces Viridochromogenes Tu57 is the principal producer of avilamycin A. aviG1, a putative methyltransferase gene, was detected in the avilamycin biosynthetic gene cluster. To determine the function of aviG1, a targeted gene inactivation experiment was performed. The resulting chromosomal mutant, carrying an in-frame deletion in aviG1, was deficient in avilamycin production. aviG1 was used to complement an eryBIII mutant of the erythromycin A producer Saccharopolyspora erythraea [Gaisser, S., Bohm, G. A., Doumith, M., Raynal, M. C., Dhillon, N., Cortes, J. & Leadlay, P. F. (1998) R12 . Mol Gen Genet 258, 78–88]. The presence of erythromycin A in the culture supernatant of the complemented mutant indicated that L-mycarose biosynthesis could be restored and that AviG1 could take over the function of the C-methyltransferase EryBIII.

  • An ATP-binding cassette transporter and two rRNA methyltransferases are involved in resistance to avilamycin in the producer organism Streptomyces Viridochromogenes Tü57.
    Antimicrobial agents and chemotherapy, 2001
    Co-Authors: Gabriele Weitnauer, Sibylle Gaisser, Axel Trefzer, Sigrid Stockert, Lucy Westrich, Luis M. Quirós, Carmen Méndez, José A. Salas, Andreas Bechthold
    Abstract:

    Avilamycins (Fig. ​(Fig.1),1), produced by Streptomyces Viridochromogenes Tu57, belong to the orthosomycin class of antibiotics (7). Avilamycins as well as other orthosomycins inhibit the growth of multidrug-resistant gram-positive bacteria (7, 30). One member of this class, the compound everninomicin (also called {"type":"entrez-protein","attrs":{"text":"SCH27899","term_id":"1052962409"}}SCH27899 or ziracin), may provide an alternative to vancomycin and other antibiotics for the treatment of many infectious diseases (8, 12, 13, 17, 19, 28). Avilamycin A has been proposed to be a translation inhibitor binding to the 30S ribosomal subunit, and it was suggested that the drug acts by preventing the attachment of tRNA to the ribosomes (29). In contrast, everninomicin and avilamycin A were shown to bind exclusively to the 50S ribosomal subunit (20). Recently a clinical isolate of Streptococcus pneumoniae that showed decreased susceptibility to everninomicin was detected, and it was shown that the resistance was due to a point mutation that causes an Ile52-Ser substitution in ribosomal protein L16 (2). It was speculated that everninomicin interacts with rRNA and that this interaction is potentiated by an additional interaction with protein L16. Since S. Viridochromogenes Tu57 is also resistant to the inhibitory action of its own antibiotic, an understanding of its mechanism of resistance may give further information on the mode of action of orthosomycin antibiotics. We have reported the cloning of a 65-kb region of DNA from S. Viridochromogenes Tu57 containing genes (aviD, aviE, and aviM) encoding proteins involved in the biosynthesis of avilamycin A (14). Here we present the cloning and characterization of DNA fragments from the avilamycin biosynthetic gene cluster which, after transformation into Streptomyces lividans, conferred avilamycin resistance. Sequencing and expression of the corresponding genes revealed that they code for an ATP-binding cassette (ABC) transporter system and two rRNA methyltransferases. FIG. 1 Structure of avilamycin A.

Nicholas P. Mulholland - One of the best experts on this subject based on the ideXlab platform.