The mcyF gene of the microcystin biosynthetic gene cluster from Microcystis aeruginosa encodes an aspartate racemase

Microcystins are hepatotoxic, non-ribosomal peptides produced by several genera of freshwater cyanobacteria. Among other enzymic activities, in particular those of peptide synthetases and polyketide synthases, microcystin biosynthesis requires racemases that provide d-aspartate and d-glutamate. Here, we report on the cloning, expression and characterization of an open reading frame, mcyF, that is part of the mcy gene cluster involved in microcystin biosynthesis in the Microcystis aeruginosa strain PCC 7806. Conserved amino acid sequence motifs suggest a function of the McyF protein as an aspartate racemase. Heterologous expression of mcyF in the unicellular cyanobacterium Synechocystis PCC 6803 yielded an active His6-tagged protein that was purified to homogeneity by Ni2+-nitriloacetate affinity chromatography. The purified recombinant protein racemized in a pyridoxal-5′-phosphate-independent manner l-aspartate, but not l-glutamate. Furthermore, we have identified a putative glutamate racemase gene that is located outside the mcy gene cluster in the M. aeruginosa PCC 7806 genome. Whereas homologues of this glutamate racemase gene are present in all the Microcystis strains examined, mcyF could only be detected in microcystin-producing strains.

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The Gas Vesicle Gene Cluster from Microcystis aeruginosa and DNA Rearrangements That Lead to Loss of Cell Buoyancy

Journal of Bacteriology ◽

10.1128/jb.186.8.2355-2365.2004 ◽

2004 ◽

Vol 186 (8) ◽

pp. 2355-2365 ◽

Cited By ~ 79

Author(s):

Alyssa Mlouka ◽

Katia Comte ◽

Anne-Marie Castets ◽

Christiane Bouchier ◽

Nicole Tandeau de Marsac

Keyword(s):

Electron Microscopy ◽

Gene Cluster ◽

Microcystis Aeruginosa ◽

Gas Vesicles ◽

Structural Protein ◽

Dna Rearrangements ◽

Unicellular Cyanobacterium ◽

Laboratory Cultures ◽

Insertion Elements ◽

Freshwater Environments

ABSTRACT Microcystis aeruginosa is a planktonic unicellular cyanobacterium often responsible for seasonal mass occurrences at the surface of freshwater environments. An abundant production of intracellular structures, the gas vesicles, provides cells with buoyancy. A 8.7-kb gene cluster that comprises twelve genes involved in gas vesicle synthesis was identified. Ten of these are organized in two operons, gvpAI AII AIII CNJX and gvpKFG, and two, gvpV and gvpW, are individually expressed. In an attempt to elucidate the basis for the frequent occurrence of nonbuoyant mutants in laboratory cultures, four gas vesicle-deficient mutants from two strains of M. aeruginosa, PCC 7806 and PCC 9354, were isolated and characterized. Their molecular analysis unveiled DNA rearrangements due to four different insertion elements that interrupted gvpN, gvpV, or gvpW or led to the deletion of the gvpAI -AIII region. While gvpA, encoding the major gas vesicle structural protein, was expressed in the gvpN, gvpV, and gvpW mutants, immunodetection revealed no corresponding GvpA protein. Moreover, the absence of a gas vesicle structure was confirmed by electron microscopy. This study brings out clues concerning the process driving loss of buoyancy in M. aeruginosa and reveals the requirement for gas vesicle synthesis of two newly described genes, gvpV and gvpW.

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Isolation, Characterization, and Heterologous Expression of the Novel Lantibiotic Epicidin 280 and Analysis of Its Biosynthetic Gene Cluster

Applied and Environmental Microbiology ◽

10.1128/aem.64.9.3140-3146.1998 ◽

1998 ◽

Vol 64 (9) ◽

pp. 3140-3146 ◽

Cited By ~ 84

Author(s):

Christoph Heidrich ◽

Ulrike Pag ◽

Michaele Josten ◽

Jörg Metzger ◽

Ralph W. Jack ◽

...

Keyword(s):

Amino Acid ◽

Gene Cluster ◽

Staphylococcus Epidermidis ◽

High Performance ◽

Sequence Similarity ◽

Biosynthetic Gene Cluster ◽

Open Reading Frames ◽

Reverse Phase ◽

Reading Frame ◽

Reading Frames

ABSTRACT Epicidin 280 is a novel type A lantibiotic produced byStaphylococcus epidermidis BN 280. During C18reverse-phase high-performance liquid chromatography two epicidin 280 peaks were obtained; the two compounds had molecular masses of 3,133 ± 1.5 and 3,136 ± 1.5 Da, comparable antibiotic activities, and identical amino acid compositions. Amino acid sequence analysis revealed that epicidin 280 exhibits 75% similarity to Pep5. The strains that produce epicidin 280 and Pep5 exhibit cross-immunity, indicating that the immunity peptides cross-function in antagonization of both lantibiotics. The complete epicidin 280 gene cluster was cloned and was found to comprise at least five open reading frames (eciI, eciA, eciP,eciB, and eciC, in that order). The proteins encoded by these open reading frames exhibit significant sequence similarity to the biosynthetic proteins of the Pep5 operon ofStaphylococcus epidermidis 5. A gene for an ABC transporter, which is present in the Pep5 gene cluster but is necessary only for high yields (G. Bierbaum, M. Reis, C. Szekat, and H.-G. Sahl, Appl. Environ. Microbiol. 60:4332–4338, 1994), was not detected. Instead, upstream of the immunity gene eciI we found an open reading frame, eciO, which could code for a novel lantibiotic modification enzyme involved in reduction of an N-terminally located oxopropionyl residue. Epicidin 280 produced by the heterologous host Staphylococcus carnosus TM 300 after introduction of eciIAPBC (i.e., no eciO was present) behaved homogeneously during reverse-phase chromatography.

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Anacyclamide D8P, a prenylated cyanobactin from a Sphaerospermopsis sp. cyanobacterium

10.26434/chemrxiv.5346739.v1 ◽

2017 ◽

Cited By ~ 1

Author(s):

Joana Martins ◽

Niina Leikoski ◽

Matti Wahlsten ◽

Joana Azevedo ◽

Jorge Antunes ◽

...

Keyword(s):

Gene Cluster ◽

Cyclic Peptides ◽

Biosynthetic Gene Cluster ◽

The Novel ◽

Tyrosine Residue ◽

Biosynthetic Gene ◽

Post Translational Modification ◽

Biological Assays ◽

Mass Spectrometric Data ◽

Spectrometric Data

Cyanobactins are a family of linear and cyclic peptides produced through the post-translational modification of short precursor peptides. Anacyclamides are macrocyclic cyanobactins with a highly diverse sequence that are common in the genus Anabaena. A mass spectrometry-based screening of potential cyanobactin producers led to the discovery of a new prenylated member of this family of compounds, anacyclamide D8P (1), from Sphaerospermopsis sp. LEGE 00249. The anacyclamide biosynthetic gene cluster (acy) encoding the novel macrocyclic prenylated cyanobactin, was sequenced. Heterologous expression of the acy gene cluster in Escherichia coli established the connection between genomic and mass spectrometric data. Unambiguous establishment of the type and site of prenylation required the full structural elucidation of 1 using Nuclear Magnetic Resonance (NMR), which demonstrated that a forward prenylation occurred on the tyrosine residue. Compound 1 was tested in pharmacologically or ecologically relevant biological assays and revealed moderate antimicrobial activity towards the fouling bacterium Halomonas aquamarina CECT 5000.

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