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Heterologous expression of peptidyl-Lys metallopeptidase of Armillaria mellea and mutagenic analysis of the recombinant peptidase.

ABSTRACT: A method to express, purify and modify the Peptidyl-Lys metallopeptidase (LysN) ofArmillaria melleainPichia pastoriswas developed to enable functional studies of the protease. Based on prior work, we propose a mechanism of action of LysN. Catalytic residues were investigated by site-directed mutagenesis. As anticipated, these mutations resulted in significantly reduced catalytic rates. Additionally, based on molecular modelling eleven mutants were designed to have altered substrate specificity. The S1' binding pocket of LysN is quite narrow and lined with negative charge to specifically accommodate lysine. To allow for arginine specificity in S1', it was proposed to extend the S1' binding pocket by mutagenesis, however the resulting mutant did not show any activity with arginine in P1'. Two mutants, A101D and T105D, showed increased specificity towards arginine in subsites S2'-S4' compared to the wild type protease. We speculate that the increased specificity to result from the additional negative charge which attract and interact with positively charged residues better than the wild type.

SUBMITTER: Odum AS

PROVIDER: S-EPMC4885931 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Armillaria mellea

Project description:Armillaria mellea overview

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Project description:Armillaria mellea is a honey mushroom often used in the traditional Chinese medicine "Tianma". Currently, this medicinal mushroom is also used as a dietary supplement in numerous Western and Eastern countries. Armillarikin was isolated from A. mellea, and we previously discovered that it induced cytotoxicity in human leukemia cells. In this study, we further investigated the cytotoxicity of armillarikin against liver and intrahepatic bile duct cancer cells. Armillarikin was cytotoxic against human hepatocellular carcinoma Huh7, HA22T, and HepG2 cells based on the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium and alamarBlue(®) assays. Armillarikin treatment also induced the collapse of the mitochondrial transmembrane potential of these cells. Furthermore, armillarikin-induced apoptotic cell death was demonstrated by sub-G1 chromosomal DNA formation by using flow cytometry. In addition, the apoptosis was inhibited by the pan-caspase inhibitor, Z-VAD-fmk. Immunoblotting also revealed the armillarikin-induced activation of procaspase-3, -8, and -9 and upregulation of the apoptosis- and cell cycle arrest-related phospho-histones 2 and 3, respectively. Moreover, reactive oxygen species scavengers also inhibited the armillarikin-induced apoptosis in human hepatocellular carcinoma, suggesting that reactive oxygen species formation played an important role in the armillarikin-induced apoptosis of human hepatocellular carcinoma. In conclusion, our study indicates the potential of armillarikin as an effective agent for hepatoma or leukemia therapies.

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Project description:Armillaria mellea 131 Genome sequencing

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A Fivefold Parallelized Biosynthetic Process Secures Chlorination of Armillaria mellea (Honey Mushroom) Toxins.

Project description:The basidiomycetous tree pathogen Armillaria mellea (honey mushroom) produces a large variety of structurally related antibiotically active and phytotoxic natural products, referred to as the melleolides. During their biosynthesis, some members of the melleolide family of compounds undergo monochlorination of the aromatic moiety, whose biochemical and genetic basis was not known previously. This first study on basidiomycete halogenases presents the biochemical in vitro characterization of five flavin-dependent A. mellea enzymes (ArmH1 to ArmH5) that were heterologously produced in Escherichia coli. We demonstrate that all five enzymes transfer a single chlorine atom to the melleolide backbone. A 5-fold, secured biosynthetic step during natural product assembly is unprecedented. Typically, flavin-dependent halogenases are categorized into enzymes acting on free compounds as opposed to those requiring a carrier-protein-bound acceptor substrate. The enzymes characterized in this study clearly turned over free substrates. Phylogenetic clades of halogenases suggest that all fungal enzymes share an ancestor and reflect a clear divergence between ascomycetes and basidiomycetes.

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A native promoter and inclusion of an intron is necessary for efficient expression of GFP or mRFP in Armillaria mellea.

Project description:Armillaria mellea is a significant pathogen that causes Armillaria root disease on numerous hosts in forests, gardens and agricultural environments worldwide. Using a yeast-adapted pCAMBIA0380 Agrobacterium vector, we have constructed a series of vectors for transformation of A. mellea, assembled using yeast-based recombination methods. These have been designed to allow easy exchange of promoters and inclusion of introns. The vectors were first tested by transformation into basidiomycete Clitopilus passeckerianus to ascertain vector functionality then used to transform A. mellea. We show that heterologous promoters from the basidiomycetes Agaricus bisporus and Phanerochaete chrysosporium that were used successfully to control the hygromycin resistance cassette were not able to support expression of mRFP or GFP in A. mellea. The endogenous A. mellea gpd promoter delivered efficient expression, and we show that inclusion of an intron was also required for transgene expression. GFP and mRFP expression was stable in mycelia and fluorescence was visible in transgenic fruiting bodies and GFP was detectable in planta. Use of these vectors has been successful in giving expression of the fluorescent proteins GFP and mRFP in A. mellea, providing an additional molecular tool for this pathogen.

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Transcriptome analysis of genes involved in defence response in Polyporus umbellatus with Armillaria mellea infection.

Project description:Polyporus umbellatus, a species symbiotic with Armillaria mellea and it also exhibits substantial defence response to Armillaria mellea infection. There are no genomics resources databases for understanding the molecular mechanism underlying the infection stress of P. umbellatus. Therefore, we performed a large-scale transcriptome sequencing of this fungus with A. mellea infection using Illumina sequencing technology. The assembly of the clean reads resulted in 120,576 transcripts, including 38,444 unigenes. Additionally, we performed a gene expression profiling analysis upon infection treatment. The results indicated significant differences in the gene expression profiles between the control and the infection group. In total, 10933 genes were identified between the two groups. Based on the differentially expressed genes, a Gene Ontology annotation analysis showed many defence-relevant categories. Meanwhile, the Kyoto Encyclopedia of Genes and Genomes pathway analysis uncovered some important pathways. Furthermore, the expression patterns of 13 putative genes that are involved in defence response resulting from quantitative real-time PCR were consistent with their transcript abundance changes as identified by RNA-seq. The sequenced genes covered a considerable proportion of the P. umbellatus transcriptome, and the expression results may be useful to strengthen the knowledge on the defence response of this fungus defend against Armillaria mellea invasion.

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Project description:Armillaria mellea DSM 3731 Genome sequencing

| PRJNA196228 | ENA

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Project description:Armillaria mellea ELDO17 Transcriptome - A_mel_RNA

| PRJNA568830 | ENA