scholarly journals Structural Requirements for the Activity of the MirB Ferrisiderophore Transporter of Aspergillus fumigatus

2012 ◽  
Vol 11 (11) ◽  
pp. 1333-1344 ◽  
Author(s):  
Isabelle Raymond-Bouchard ◽  
Cassandra S. Carroll ◽  
Jason R. Nesbitt ◽  
Kevin A. Henry ◽  
Linda J. Pinto ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Aspergillus Fumigatus ◽  
Transmembrane Protein ◽  
Site Directed Mutagenesis ◽  
Wild Type ◽  
Content Type ◽  
Mutant Proteins ◽  
Opportunistic Fungal Pathogen ◽  
Triacetylfusarinine C ◽  
Siderophore Transporter

ABSTRACTSiderophores have been identified as virulence factors in the opportunistic fungal pathogenAspergillus fumigatus. The 14-pass transmembrane protein MirB is postulated to function as a siderophore transporter, responsible for uptake of the hydroxamate siderophoreN,N′,N″-triacetylfusarinine C (TAFC). Our aim was to identify amino acids ofA. fumigatusMirB that are crucial for uptake of TAFC. Site-directed mutagenesis was used to create MirB mutants. Expression of wild-type and mutant proteins in theSaccharomyces cerevisiaestrain PHY14, which lacks endogenous siderophore transporters, was confirmed by Western blotting. TAFC transport assays using55Fe-labeled TAFC and growth assays with Fe-TAFC as the sole iron source identified alanine 125, tyrosine 577, loop 3, and the second half of loop 7 (Loop7Del2) as crucial for function, since their substitution or deletion abrogated uptake completely. Wild-type MirB transported ferricrocin and coprogen as well as TAFC but not ferrichrysin. MirB was localized by fluorescence microscopy using antisera raised against a MirB extracellular loop peptide. Immunofluorescence microscopy showed that in yeast, wild-type MirB had a punctate distribution under the plasma membrane, as did the A125D and Y577A strains, indicating that the defect in transport of these mutants was unlikely to be due to mislocalization or degradation. MirB immunolocalization inA. fumigatusshowed that the transporter was found in vesicles which cycled between the cytoplasm and the plasma membrane and was concentrated at the hyphal tips. The location of MirB was not influenced by the presence of the siderophore TAFC but was sensitive to internal iron stores.

scholarly journals SidL, an Aspergillus fumigatus Transacetylase Involved in Biosynthesis of the Siderophores Ferricrocin and Hydroxyferricrocin

2011 ◽  
Vol 77 (14) ◽  
pp. 4959-4966 ◽  
Author(s):  
Michael Blatzer ◽  
Markus Schrettl ◽  
Bettina Sarg ◽  
Herbert H. Lindner ◽  
Kristian Pfaller ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Fluorescent Protein ◽  
Iron Starvation ◽  
Fungal Virulence ◽  
Content Type ◽  
Siderophore Biosynthesis ◽  
Opportunistic Fungal Pathogen ◽  
Triacetylfusarinine C ◽  
Green Fluorescent ◽  
Biosynthetic Machinery

ABSTRACTThe opportunistic fungal pathogenAspergillus fumigatusproduces four types of siderophores, low-molecular-mass iron chelators: it excretes fusarinine C (FsC) and triacetylfusarinine C (TAFC) for iron uptake and accumulates ferricrocin (FC) for hyphal and hydroxyferricrocin (HFC) for conidial iron distribution and storage. Siderophore biosynthesis has recently been shown to be crucial for fungal virulence. Here we identified a new component of the fungal siderophore biosynthetic machinery: AFUA_1G04450, termed SidL. SidL is conserved only in siderophore-producing ascomycetes and shows similarity to transacylases involved in bacterial siderophore biosynthesis and theN5-hydroxyornithine:anhydromevalonyl coenzyme A-N5-transacylase SidF, which is essential for TAFC biosynthesis. Inactivation of SidL inA. fumigatusdecreased FC biosynthesis during iron starvation and completely blocked FC biosynthesis during iron-replete growth. In agreement with these findings, SidL deficiency blocked conidial accumulation of FC-derived HFC under iron-replete conditions, which delayed germination and decreased the size of conidia and their resistance to oxidative stress. Remarkably, thesidLgene is not clustered with other siderophore-biosynthetic genes, and its expression is not affected by iron availability. Tagging of SidL with enhanced green fluorescent protein suggested a cytosolic localization of the FC-biosynthetic machinery. Taken together, these data suggest that SidL is a constitutively activeN5-hydroxyornithine-acetylase required for FC biosynthesis, in particular under iron-replete conditions. Moreover, this study revealed the unexpected complexity of siderophore biosynthesis, indicating the existence of an additional, iron-repressedN5-hydroxyornithine-acetylase.

scholarly journals Pharmacodynamics of Itraconazole against Aspergillus fumigatus in anIn VitroModel of the Human Alveolus: Perspectives on the Treatment of Triazole-Resistant Infection and Utility of Airway Administration

2012 ◽  
Vol 56 (8) ◽  
pp. 4146-4153 ◽  
Author(s):  
Zaid Al-Nakeeb ◽  
Ajay Sudan ◽  
Adam R. Jeans ◽  
Lea Gregson ◽  
Joanne Goodwin ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Therapeutic Strategies ◽  
Wild Type ◽  
Content Type ◽  
Exposure Response ◽  
Prevention And Treatment ◽  
Resistant Infection ◽  
Resistant Strains ◽  
Type Strains

ABSTRACTItraconazole is used for the prevention and treatment of infections caused byAspergillus fumigatus. An understanding of the pharmacodynamics of itraconazole against wild-type and triazole-resistant strains provides a basis for innovative therapeutic strategies for treatment of infections. Anin vitromodel of the human alveolus was used to define the pharmacodynamics of itraconazole. Galactomannan was used as a biomarker. The effect of systemic and airway administration of itraconazole was assessed, as was a combination of itraconazole administered to the airway and systemically administered 5FC. Systemically administered itraconazole against the wild type induced a concentration-dependent decline in galactomannan in the alveolar and endothelial compartments. No exposure-response relationships were apparent for the L98H, M220T, or G138C mutant. The administration of itraconazole to the airway resulted in comparable exposure-response relationships to those observed with systemic therapy. This was achieved without detectable concentrations of drug within the endothelial compartment. The airway administration of itraconazole resulted in a definite but submaximal effect in the endothelial compartment against the L98H mutant. The administration of 5FC resulted in a concentration-dependent decline in galactomannan in both the alveolar and endothelial compartments. The combination of airway administration of itraconazole and systemically administered 5FC was additive. Systemic administration of itraconazole is ineffective against Cyp51 mutants. The airway administration of itraconazole is effective for the treatment of wild-type strains and appears to have some activity against the L98H mutants. Combination with other agents, such as 5FC, may enable the attainment of near-maximal antifungal activity.

scholarly journals Lateral diffusion of wild-type and mutant Ld antigens in L cells.

1984 ◽  
Vol 99 (6) ◽  
pp. 2333-2335 ◽  
Author(s):  
M Edidin ◽  
M Zuniga
Keyword(s):  
Plasma Membrane ◽  
Diffusion Coefficients ◽  
Transmembrane Protein ◽  
Transmembrane Proteins ◽  
Lateral Diffusion ◽  
Cytoplasmic Domain ◽  
Histocompatibility Antigen ◽  
Wild Type ◽  
Major Histocompatibility Antigen ◽  
Cytoplasmic Side

We have compared the lateral diffusion of intact transmembrane proteins, wild-type H-2Ld antigens, with that of mutants truncated in the cytoplasmic domain. Diffusion coefficients and mobile fractions were similar for all molecules examined, from wild-type Ld antigens with 31 residues on the cytoplasmic side of the plasma membrane to mutants with only four residues in the cytoplasmic domain. This result limits ways in which the lateral diffusion of a major histocompatibility antigen, a transmembrane protein, can be constrained by interactions with other molecules.

Identification of ferrichrome- and ferrioxamine B-mediated iron uptake by Aspergillus fumigatus

2016 ◽  
Vol 473 (9) ◽  
pp. 1203-1213 ◽  
Author(s):  
Yong-Sung Park ◽  
Ju-Yeon Kim ◽  
Cheol-Won Yun
Keyword(s):  
Gene Expression ◽  
Plasma Membrane ◽  
Aspergillus Fumigatus ◽  
Virulence Factors ◽  
Membrane Transporters ◽  
Yeast Cells ◽  
Double Deletion ◽  
Ferrioxamine B ◽  
Uptake Activity ◽  
Opportunistic Fungal Pathogen

Aspergillus fumigatus is an opportunistic fungal pathogen for immunocompromised patients, and genes involved in siderophore metabolism have been identified as virulence factors. Recently, we identified the membrane transporters sit1 and sit2, which are putative virulence factors of A. fumigatus; sit1 and sit2 are homologous to yeast Sit1, and sit1 and sit2 gene expression was up-regulated after iron depletion. When expressed heterologously in Saccharomyces cerevisiae, sit1 and sit2 were localized to the plasma membrane; sit1 efficiently complemented ferrichrome (FC) and ferrioxamine B (FOB) uptake in yeast cells, whereas sit2 complemented only FC uptake. Deletion of sit1 resulted in a decrease in FOB and FC uptake, and deletion of sit2 resulted in a decrease in FC uptake in A. fumigatus. It is of interest that a sit1 and sit2 double-deletion mutant resulted in a synergistic decrease in FC uptake activity. Both sit1 and sit2 were localized to the plasma membrane in A. fumigatus. The expression levels of the sit1 and sit2 genes were dependent on hapX under low-but not high-iron conditions. Furthermore, mirB, and sidA gene expression was up-regulated and sreA expression down-regulated when sit1 and sit2 were deleted. Although sit1 and sit2 failed to affect mouse survival rate, these genes affected conidial killing activity. Taken together, our results suggest that sit1 and sit2 are siderophore transporters and putative virulence factors localized to the plasma membrane.

scholarly journals Aspergillus fumigatus Acetate Utilization Impacts Virulence Traits and Pathogenicity

mBio ◽  
2021 ◽  
Author(s):  
Laure Nicolas Annick Ries ◽  
Patricia Alves de Castro ◽  
Lilian Pereira Silva ◽  
Clara Valero ◽  
Thaila Fernanda dos Reis ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Fungal Pathogen ◽  
Carbon Sources ◽  
Body Fluids ◽  
Peripheral Tissues ◽  
Content Type ◽  
Virulence Traits ◽  
Acetate Utilization ◽  
Opportunistic Fungal Pathogen

Aspergillus fumigatus is an opportunistic fungal pathogen in humans. During infection, A. fumigatus is predicted to use host carbon sources, such as acetate, present in body fluids and peripheral tissues, to sustain growth and promote colonization and invasion.

scholarly journals Key Role of Cysteine Residues in Catalysis and Subcellular Localization of Sulfur Oxygenase-Reductase of Acidianus tengchongensis

2005 ◽  
Vol 71 (2) ◽  
pp. 621-628 ◽  
Author(s):  
Zhi-Wei Chen ◽  
Cheng-Ying Jiang ◽  
Qunxin She ◽  
Shuang-Jiang Liu ◽  
Pei-Jin Zhou
Keyword(s):  
Cytoplasmic Membrane ◽  
Sulfur Oxidation ◽  
Site Directed Mutagenesis ◽  
Cysteine Residues ◽  
Wild Type ◽  
Immune Electron Microscopy ◽  
Mutant Proteins ◽  
Close Proximity ◽  
Catalytic Sites

ABSTRACT Analysis of known sulfur oxygenase-reductases (SORs) and the SOR-like sequences identified from public databases indicated that they all possess three cysteine residues within two conserved motifs (V-G-P-K-V-C31 and C101-X-X-C104; numbering according to the Acidianus tengchongensis numbering system). The thio-modifying reagent N-ethylmaleimide and Zn2+ strongly inhibited the activities of the SORs of A. tengchongensis, suggesting that cysteine residues are important. Site-directed mutagenesis was used to construct four mutant SORs with cysteines replaced by serine or alanine. The purified mutant proteins were investigated in parallel with the wild-type SOR. Replacement of any cysteine reduced SOR activity by 98.4 to 100%, indicating that all the cysteine residues are crucial to SOR activities. Circular-dichroism and fluorescence spectrum analyses revealed that the wild-type and mutant SORs have similar structures and that none of them form any disulfide bond. Thus, it is proposed that three cysteine residues, C31 and C101-X-X-C104, in the conserved domains constitute the putative binding and catalytic sites of SOR. Furthermore, enzymatic activity assays of the subcellular fractions and immune electron microscopy indicated that SOR is not only present in the cytoplasm but also associated with the cytoplasmic membrane of A. tengchongensis. The membrane-associated SOR activity was colocalized with the activities of sulfite:acceptor oxidoreductase and thiosulfate:acceptor oxidoreductase. We tentatively propose that these enzymes are located in close proximity on the membrane to catalyze sulfur oxidation in A. tengchongensis.

scholarly journals ThemtfATranscription Factor Gene Controls Morphogenesis, Gliotoxin Production, and Virulence in the Opportunistic Human Pathogen Aspergillus fumigatus

2014 ◽  
Vol 13 (6) ◽  
pp. 766-775 ◽  
Author(s):  
Timothy D. Smith ◽  
Ana M. Calvo
Keyword(s):  
Aspergillus Fumigatus ◽  
Protease Activity ◽  
Galleria Mellonella ◽  
Molecular Genetic ◽  
Colony Growth ◽  
Infection Model ◽  
Slight Reduction ◽  
Wild Type ◽  
Content Type ◽  
Factor Gene

ABSTRACTAspergillus fumigatusis the leading causative agent of invasive aspergillosis (IA). The number of cases is on the rise, with mortality rates as high as 90% among immunocompromised patients. Molecular genetic studies inA. fumigatuscould provide novel targets to potentially set the basis for antifungal therapies. In the current study, we investigated the role of the transcription factor genemtfAinA. fumigatus. Our results revealed thatmtfAplays a role in the growth and development of the fungus. Deletion or overexpression ofmtfAleads to a slight reduction in colony growth, as well as a reduction in conidiation levels, in the overexpression strain compared to the wild-type strain. Furthermore, production of the secondary metabolite gliotoxin increased whenmtfAwas overexpressed, coinciding with an increase in the transcription levels of the gliotoxin genesgliZandgliPwith respect to the wild type. In addition, our study showed thatmtfAis also necessary for normal protease activity inA. fumigatus; deletion ofmtfAresulted in a reduction of protease activity compared to wild-type levels. Importantly, the absence ofmtfAcaused a decrease in virulence in theGalleria mellonellainfection model, indicating thatmtfAis necessary forA. fumigatuswild-type pathogenesis.

scholarly journals In Vivo Efficacy of Liposomal Amphotericin B against Wild-Type and Azole-Resistant Aspergillus fumigatus Isolates in Two Different Immunosuppression Models of Invasive Aspergillosis

2017 ◽  
Vol 61 (6) ◽  
Author(s):  
Seyedmojtaba Seyedmousavi ◽  
Johan W. Mouton ◽  
Willem J. G. Melchers ◽  
Paul E. Verweij
Keyword(s):  
Invasive Aspergillosis ◽  
Aspergillus Fumigatus ◽  
Amphotericin B ◽  
Liposomal Amphotericin ◽  
Treated Group ◽  
Liposomal Amphotericin B ◽  
Wild Type ◽  
Resistance Mutations ◽  
Content Type

ABSTRACT Using an immunocompetent murine model of invasive aspergillosis (IA), we previously reported that the efficacy of liposomal amphotericin B (L-AmB) (Ambisome) is not hampered by the presence of azole resistance mutations in Aspergillus fumigatus (S. Seyedmousavi, W. J. G. Melchers, J. W. Mouton, and P. E. Verweij, Antimicrob Agents Chemother 57:1866–1871, 2013, https://doi.org/10.1128/AAC.02226-12 ). We here investigated the role of immune suppression, i.e., neutropenia and steroid treatment, in L-AmB efficacy in mice infected with wild-type (WT) A. fumigatus and with azole-resistant A. fumigatus harboring a TR34/L98H mutation in the cyp-51A gene. Survival of treated animals at day 14 in both immunosuppressed models was significantly better than that of nontreated controls. A dose-response relationship was observed that was independent of the azole-resistant mechanism and the immunosuppression method used. In the neutropenic model, 100% survival was reached at an L-AmB dose of 16 mg/kg of body weight for the WT strain and the TR34/L98H isolate. In the steroid-treated group, 90.9% survival and 100% survival were achieved for the WT isolate and the TR34/L98H isolate with an L-AmB dose of 16 mg/kg, respectively. The 50% effective dose (ED50) was 1.40 mg/kg (95% confidence interval [CI], 0.66 to 3.00 mg/kg) for the WT isolate and 1.92 mg/kg (95% CI, 0.60 to 6.17 mg/kg) for the TR34/L98H isolate in the neutropenic model and was 2.40 mg/kg (95% CI, 1.93 to 2.97 mg/kg) for the WT isolate and 2.56 mg/kg (95% CI, 1.43 to 4.56 mg/kg) for the TR34/L98H isolate in the steroid-treated group. Overall, there were no significant differences between the two different immunosuppressed conditions in the efficacy of L-AmB against the wild-type and azole-resistant isolates (P > 0.9). However, the required L-AmB exposure was significantly higher than that seen in the immunocompetent model.

scholarly journals S279 Point Mutations in Candida albicans Sterol 14-α Demethylase (CYP51) ReduceIn VitroInhibition by Fluconazole

2012 ◽  
Vol 56 (4) ◽  
pp. 2099-2107 ◽  
Author(s):  
Andrew G. S. Warrilow ◽  
Jonathan G. L. Mullins ◽  
Claire M. Hull ◽  
Josie E. Parker ◽  
David C. Lamb ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Point Mutations ◽  
Triazole Ring ◽  
Wild Type ◽  
Protein Activity ◽  
Content Type ◽  
Mutant Proteins ◽  
Type Protein ◽  
Wild Type Protein ◽  
Binding Spectra

ABSTRACTThe effects of S279F and S279Y point mutations inCandida albicansCYP51 (CaCYP51) on protein activity and on substrate (lanosterol) and azole antifungal binding were investigated. Both S279F and S279Y mutants bound lanosterol with 2-fold increased affinities (Ks, 7.1 and 8.0 μM, respectively) compared to the wild-type CaCYP51 protein (Ks, 13.5 μM). The S279F and S279Y mutants and the wild-type CaCYP51 protein bound fluconazole, voriconazole, and itraconazole tightly, producing typical type II binding spectra. However, the S279F and S279Y mutants had 4- to 5-fold lower affinities for fluconazole, 3.5-fold lower affinities for voriconazole, and 3.5- to 4-fold lower affinities for itraconazole than the wild-type CaCYP51 protein. The S279F and S279Y mutants gave 2.3- and 2.8-fold higher 50% inhibitory concentrations (IC50s) for fluconazole in a CYP51 reconstitution assay than the wild-type protein did. The increased fluconazole resistance conferred by the S279F and S279Y point mutations appeared to be mediated through a combination of a higher affinity for substrate and a lower affinity for fluconazole. In addition, lanosterol displaced fluconazole from the S279F and S279Y mutants but not from the wild-type protein. Molecular modeling of the wild-type protein indicated that the oxygen atom of S507 interacts with the second triazole ring of fluconazole, assisting in orientating fluconazole so that a more favorable binding conformation to heme is achieved. In contrast, in the two S279 mutant proteins, this S507-fluconazole interaction is absent, providing an explanation for the higherKdvalues observed.

scholarly journals 11 Study of Polynucleotide Kinase/Phosphatase (PNKP) Mutations Found in a Patient with Microcephaly, Seizures, and Developmental Delay (MCSZ) and Glioblastoma

2018 ◽  
Vol 45 (S3) ◽  
pp. S2-S2
Author(s):  
Bingcheng Jiang ◽  
Chibawanye I. Ene ◽  
Bonnie Cole ◽  
Jeff Ojemann ◽  
Sarah Leary ◽  
...  
Keyword(s):  
Human Cancer ◽  
Neurodevelopmental Disorder ◽  
Site Directed Mutagenesis ◽  
Expression Vectors ◽  
Wild Type ◽  
Double Mutation ◽  
Mutant Proteins ◽  
Human Cancer Cell Lines ◽  
Mammalian Expression ◽  
Polynucleotide Kinase

The enzyme polynucleotide kinase/phosphatase (PNKP) plays a key role in DNA repair by resolving the chemistry at DNA strand breaks. Mutations in PNKP (chromosome 19q13.4) are known to cause MCSZ, a serious neurodevelopmental disorder, but to date there has been no link to cancer initiation or progression. However, a child with MCSZ recently presented at Seattle Children's Hospital with a 3-cm glioblastoma. The child was shown to have two germline mutations in PNKP. To study the effects of the PNKP mutations found in this patient, we generated mutant PNKP cDNAs carrying either the individual mutations or the double mutation using site directed mutagenesis. These cDNAs were incorporated into bacterial and mammalian expression vectors. The bacterially expressed mutant proteins as well as the wild type have been purified and are undergoing testing for PNKP DNA kinase and phosphatase activity. The PNKP cDNAs, fused to GFP, were expressed in Hela and HCT116 human cancer cell lines. High-content analysis and micro-irradiation techniques are being used to determine PNKP localization within the cells and recruitment to damaged DNA. Our preliminary results indicate that the mutations alter the ratio of nuclear to cytoplasmic PNKP compared to the wild-type protein.

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