scholarly journals Characterization of the Aspergillus nidulans transporters for the siderophores enterobactin and triacetylfusarinine C

2003 ◽  
Vol 371 (2) ◽  
pp. 505-513 ◽  
Author(s):  
Hubertus HAAS ◽  
Michelle SCHOESER ◽  
Emmanuel LESUISSE ◽  
Joachim F. ERNST ◽  
Walther PARSON ◽  
...  
Keyword(s):  
Deletion Mutant ◽  
Iron Transport ◽  
Chromosomal Localization ◽  
Transport Systems ◽  
High Affinity ◽  
Intron Structure ◽  
Encoding Gene ◽  
Triacetylfusarinine C ◽  
Siderophore Transporter

The filamentous ascomyceteAspergillus nidulans produces three major siderophores: fusigen, triacetylfusarinine C, and ferricrocin. Biosynthesis and uptake of iron from these siderophores, as well as from various heterologous siderophores, is repressed by iron and this regulation is mediated in part by the transcriptional repressor SREA. Recently we have characterized a putative siderophore-transporter-encoding gene (mirA). Here we present the characterization of two further SREA- and iron-regulated paralogues (mirB and mirC), including the chromosomal localization and the complete exon/intron structure. Expression of mirA and mirB in a Saccharomyces cerevisiae strain, which lacks high affinity iron transport systems, showed that MIRA transports specifically the heterologous siderophore enterobactin and that MIRB transports exclusively the native siderophore triacetylfusarinine C. Construction and analysis of an A. nidulans mirA deletion mutant confirmed the substrate specificity of MIRA. Phylogenetic analysis of the available sequences suggests that the split of the species A. nidulans and S. cerevisiae predates the divergence of the paralogous Aspergillus siderophore transporters.

scholarly journals Vibrio Iron Transport: Evolutionary Adaptation to Life in Multiple Environments

2015 ◽  
Vol 80 (1) ◽  
pp. 69-90 ◽  
Author(s):  
Shelley M. Payne ◽  
Alexandra R. Mey ◽  
Elizabeth E. Wyckoff
Keyword(s):  
Regulatory Networks ◽  
Iron Transport ◽  
Horizontal Transmission ◽  
Essential Element ◽  
Transport Systems ◽  
Iron Binding ◽  
Content Type ◽  
High Affinity ◽  
Wide Range ◽  
Genes Encoding

SUMMARYIron is an essential element forVibriospp., but the acquisition of iron is complicated by its tendency to form insoluble ferric complexes in nature and its association with high-affinity iron-binding proteins in the host. Vibrios occupy a variety of different niches, and each of these niches presents particular challenges for acquiring sufficient iron.Vibriospecies have evolved a wide array of iron transport systems that allow the bacteria to compete for this essential element in each of its habitats. These systems include the secretion and uptake of high-affinity iron-binding compounds (siderophores) as well as transport systems for iron bound to host complexes. Transporters for ferric and ferrous iron not complexed to siderophores are also common toVibriospecies. Some of the genes encoding these systems show evidence of horizontal transmission, and the ability to acquire and incorporate additional iron transport systems may have allowedVibriospecies to more rapidly adapt to new environmental niches. While too little iron prevents growth of the bacteria, too much can be lethal. The appropriate balance is maintained in vibrios through complex regulatory networks involving transcriptional repressors and activators and small RNAs (sRNAs) that act posttranscriptionally. Examination of the number and variety of iron transport systems found inVibriospp. offers insights into how this group of bacteria has adapted to such a wide range of habitats.

scholarly journals Functional characterization of the ferroxidase, permease high-affinity iron transport complex from Candida albicans

2011 ◽  
Vol 81 (2) ◽  
pp. 473-485 ◽  
Author(s):  
Lynn Ziegler ◽  
Alaina Terzulli ◽  
Ruchi Gaur ◽  
Ryan McCarthy ◽  
Daniel J. Kosman
Keyword(s):  
Candida Albicans ◽  
Iron Transport ◽  
Functional Characterization ◽  
High Affinity ◽  
Transport Complex

scholarly journals Iron Transport Systems in Neisseria meningitidis

2004 ◽  
Vol 68 (1) ◽  
pp. 154-171 ◽  
Author(s):  
Donna Perkins-Balding ◽  
Melanie Ratliff-Griffin ◽  
Igor Stojiljkovic
Keyword(s):  
Neisseria Meningitidis ◽  
Iron Uptake ◽  
Iron Transport ◽  
Current Understanding ◽  
Transport Systems ◽  
Transport Activity ◽  
Host Proteins ◽  
Human Host ◽  
High Affinity ◽  
Dependent Transport

SUMMARY Acquisition of iron and iron complexes has long been recognized as a major determinant in the pathogenesis of Neisseria meningitidis. In this review, high-affinity iron uptake systems, which allow meningococci to utilize the human host proteins transferrin, lactoferrin, hemoglobin, and haptoglobin-hemoglobin as sources of essential iron, are described. Classic features of bacterial iron transport systems, such as regulation by the iron-responsive repressor Fur and TonB-dependent transport activity, are discussed, as well as more specific features of meningococcal iron transport. Our current understanding of how N. meningitidis acquires iron from the human host and the vaccine potentials of various components of these iron transport systems are also reviewed.

Approaches used to examine the mechanism and regulation of hexose transport in rat myoblasts

1986 ◽  
Vol 64 (11) ◽  
pp. 1081-1091 ◽  
Author(s):  
Tony D'Amore ◽  
Theodore C. Y. Lo
Keyword(s):  
Transport System ◽  
Transport Systems ◽  
Facilitated Diffusion ◽  
Hexose Transport ◽  
Plasma Membrane Vesicles ◽  
Diffusion Type ◽  
High Affinity ◽  
Isolation And Characterization ◽  
Transport Mutants

This review discusses some of the approaches and general criteria that we have used to examine the properties of the hexose transport system in undifferentiated L6 rat myoblasts. These approaches include studying the kinetics of hexose transport in whole cells and plasma membrane vesicles, the effects of various inhibitors on hexose transport, the isolation and characterization of hexose transport mutants, and the use of cytochalasin B (CB) to identify the transport component(s). Transport kinetics indicated that two transport systems are present in these cells. 2-Deoxy-D-glucose is transported primarily by the high affinity system, whereas 3-O-methyl-D-glucose is transported by the low affinity system. Furthermore, these two transport systems are inactivated to different extents by CB. CB has a higher binding affinity for the low affinity hexose transport system. The inhibitory effect of various hexose analogues also revealed the presence of two hexose transport systems. The effects of various ionophores and energy uncouplers on hexose transport suggest that the high affinity system is an active transport process, whereas the low affinity system is of the facilitated diffusion type. The high affinity system is also sensitive to sulfhydryl reagents, whereas the low affinity system is not. Further evidence for the presence of two transport systems comes from the characterization of hexose transport mutants. Two of the mutants isolated are shown to be defective in the high affinity transport system, but not in the low affinity transport system. These mutants are also defective in the CB low affinity binding site. Based on our results a tentative working model for hexose transport in L6 rat myoblasts is presented.

scholarly journals Disruption of a Novel Iron Transport System Reverses Oxidative Stress Phenotypes of a dpr Mutant Strain of Streptococcus mutans

2018 ◽  
Vol 200 (14) ◽  
Author(s):  
Tridib Ganguly ◽  
Jessica K. Kajfasz ◽  
James H. Miller ◽  
Eric Rabinowitz ◽  
Lívia C. C. Galvão ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Streptococcus Mutans ◽  
Hydroxyl Radicals ◽  
Transport System ◽  
Iron Uptake ◽  
Iron Transport ◽  
Transport Systems ◽  
Phenotypic Characterization ◽  
Content Type

ABSTRACT The Dps-like peroxide resistance protein (Dpr) is essential for H 2 O 2 stress tolerance and aerobic growth of the oral pathogen Streptococcus mutans . Dpr accumulates during oxidative stress, protecting the cell by sequestering iron ions and thereby preventing the generation of toxic hydroxyl radicals that result from the interaction of iron with H 2 O 2 . Previously, we reported that the SpxA1 and SpxA2 regulators positively regulate expression of dpr in S. mutans . Using an antibody raised against S. mutans Dpr, we confirmed at the protein level the central and cooperative nature of SpxA1 and SpxA2 regulation in Dpr production. During phenotypic characterization of the S. mutans Δ dpr strain, we observed the appearance of distinct colony variants, which sometimes lost the oxidative stress sensitivity typical of Δ dpr strains. Whole-genome sequencing of these phenotypically distinct Δ dpr isolates revealed that a putative iron transporter operon, smu995-smu998 , was a genomic hot spot with multiple single nucleotide polymorphisms identified within the different isolates. Deletion of smu995 or the entire smu995-smu998 operon in the Δ dpr background strain completely reversed the oxidative stress-sensitive phenotypes associated with dpr inactivation. Conversely, inactivation of genes encoding the ferrous iron transport system FeoABC did not alleviate phenotypes of the Δ dpr strain. Preliminary characterization of strains lacking smu995-smu998 , feoABC , and the iron/manganese transporter gene sloABC revealed the interactive nature of these three systems in iron transport but also indicated that there may be additional iron uptake systems in S. mutans . IMPORTANCE The dental caries-associated pathogen Streptococcus mutans routinely encounters oxidative stress within the human plaque biofilm. Previous studies revealed that the iron-binding protein Dpr confers protection toward oxidative stress by limiting free iron availability, which is associated with the generation of toxic hydroxyl radicals. Here, we report the identification of spontaneously occurring mutations within Δ dpr strains. Several of those mutations were mapped to the operon smu995-smu998 , revealing a previously uncharacterized system that appears to be important in iron acquisition. Disruption of the smu995-smu998 operon resulted in reversion of the stress-sensitive phenotype typical of a Δ dpr strain. Our data suggest that the Smu995-Smu998 system works along with other known metal transport systems of S. mutans , i.e., FeoABC and SloABC, to coordinate iron uptake.

scholarly journals Molecular Characterization of Two High Affinity Sulfate Transporters in Saccharomyces cerevisiae

Genetics ◽  
1997 ◽  
Vol 145 (3) ◽  
pp. 627-635 ◽  
Author(s):  
Hélène Cherest ◽  
Jean-Claude Davidian ◽  
Dominique Thomas ◽  
Vladimir Benes ◽  
Wilhelm Ansorge ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Kinetic Studies ◽  
Transport Systems ◽  
Sulfate Transport ◽  
High Affinity ◽  
Mutant Strains ◽  
Transport Kinetic ◽  
High Degree ◽  
Degree Of Similarity

Strains resistant to the toxic analogues of sulfate, selenate and chromate have been isolated. Their genetic analysis allowed us to identify four genes. One, called MET28, encodes a transcriptional factor. The three other genes, called SUL1, SUL2 and SUL3, encode proteins involved in sulfate transport. The sequence of Sul1p and Sul2p indicate that they are integral membrane proteins exhibiting, respectively, 11 and 10 transmembrane domains. Moreover, Sul1p and Sul2p share a high degree of similarity. Sulfate transport kinetic studies made with parental and mutant strains show that, as expected from genetic results, Saccharomyces cerevisiae has two high affinity sulfate transport systems. Sul3p has been shown to be involved in the transcriptional regulation of the SUL2 gene.

Extent of high-affinity iron transport systems in field isolates of rhizobia

1994 ◽  
Vol 164 (2) ◽  
pp. 177-185 ◽  
Author(s):  
E. Fabiano ◽  
G. Gualtieri ◽  
C. Pritsch ◽  
G. Polla ◽  
A. Arias
Keyword(s):  
Iron Transport ◽  
Transport Systems ◽  
Field Isolates ◽  
High Affinity
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