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International Journal of Molecular... 2012Arsenic and antimony are toxic metalloids, naturally present in the environment and all organisms have developed pathways for their detoxification. The most effective... (Review)
Review
Arsenic and antimony are toxic metalloids, naturally present in the environment and all organisms have developed pathways for their detoxification. The most effective metalloid tolerance systems in eukaryotes include downregulation of metalloid uptake, efflux out of the cell, and complexation with phytochelatin or glutathione followed by sequestration into the vacuole. Understanding of arsenic and antimony transport system is of high importance due to the increasing usage of arsenic-based drugs in the treatment of certain types of cancer and diseases caused by protozoan parasites as well as for the development of bio- and phytoremediation strategies for metalloid polluted areas. However, in contrast to prokaryotes, the knowledge about specific transporters of arsenic and antimony and the mechanisms of metalloid transport in eukaryotes has been very limited for a long time. Here, we review the recent advances in understanding of arsenic and antimony transport pathways in eukaryotes, including a dual role of aquaglyceroporins in uptake and efflux of metalloids, elucidation of arsenic transport mechanism by the yeast Acr3 transporter and its role in arsenic hyperaccumulation in ferns, identification of vacuolar transporters of arsenic-phytochelatin complexes in plants and forms of arsenic substrates recognized by mammalian ABC transporters.
Topics: ATP-Binding Cassette Transporters; Animals; Antimony; Aquaglyceroporins; Arabidopsis; Arsenic; Biological Transport; Glutathione; Humans; Leishmania; Membrane Transport Proteins; Monosaccharide Transport Proteins; Phytochelatins; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Xenopus laevis; Zebrafish
PubMed: 22489166
DOI: 10.3390/ijms13033527 -
European Journal of Immunology Aug 1995The major histocompatibility complex (MHC)-encoded transporter associated with antigen processing (TAP) delivers cytosolic peptides to the lumen of the endoplasmic...
The major histocompatibility complex (MHC)-encoded transporter associated with antigen processing (TAP) delivers cytosolic peptides to the lumen of the endoplasmic reticulum (ER) for presentation by MHC class I molecules. For the rat, it has been demonstrated that TAP polymorphism results in the selection of different sets of peptides, the nature of the C terminus being of particular importance. Here, we investigated whether TAP polymorphism in mice and humans has functional consequences for transport of peptide sets variable at the C-terminal residues. Using cell lines of H-2d, H-2k, and H-2dxk haplotype and a panel of human lymphoblastoid cell lines expressing eight different TAP alleles, we detected species-specific transport patterns, but no significant influence of TAP polymorphism on peptide selection. In addition, peptides with different core sequences were translocated to the same extent by different TAP. These results suggest that a major contribution of human TAP polymorphism to disease progression and autoimmunity is not very likely.
Topics: ATP Binding Cassette Transporter, Subfamily B, Member 2; ATP Binding Cassette Transporter, Subfamily B, Member 3; ATP-Binding Cassette Transporters; Amino Acid Sequence; Animals; Antigen Presentation; Biological Transport; Cell Line; Humans; Insecta; Lymphocytes; Major Histocompatibility Complex; Mice; Molecular Sequence Data; Peptides; Polymorphism, Genetic; Transfection
PubMed: 7664780
DOI: 10.1002/eji.1830250808 -
Biochemistry Nov 1998To obtain amino acids for growth, Lactococcus lactis uses a proteolytic system to degrade exogenous proteins such as caseins. The extracellular cell wall-attached...
To obtain amino acids for growth, Lactococcus lactis uses a proteolytic system to degrade exogenous proteins such as caseins. The extracellular cell wall-attached proteinase PrtP and the oligopeptide transport system Opp mediate the first two steps in the utilization of caseins. beta-Casein is degraded by PrtP to fragments of 5-30 amino acid residues, and only a limited number of peptides are selected from this pool for uptake via Opp. To study the specificity of Opp and the kinetics of peptide uptake in L. lactis in detail, we used the following strategy: (i) the Opp system was overexpressed; (ii) a 4-fold peptidase mutant was used that is unable to degrade KYGK; (iii) iodinated KYGK was used as the reporter peptide; (iv) libraries of peptides, in which one amino acid position is systematically varied, were used as competitive peptides; and (v) peptides were synthesized on the basis of the beta-casein degradation products, their inhibition of KYGK uptake was determined, and the uptake of these peptides was followed by high-performance liquid chromatography (HPLC). These studies indicate that (i) the Opp system can transport a broad range of peptides from 4 up to at least 18 residues with very little preference for particular side chains and (ii) the kinetics of peptide uptake differ for different substrates tested. Whereas class I peptides such as KYGK exhibit normal Michaelis-Menten kinetics, the level of uptake of the majority of peptides (class II) increases sigmoidally with concentration. Different models for explaining the apparent cooperative effects that are observed for peptide uptake are discussed.
Topics: ATP-Binding Cassette Transporters; Amino Acid Sequence; Bacterial Proteins; Biological Transport; Carrier Proteins; Caseins; Endopeptidases; Kinetics; Lactococcus lactis; Lipoproteins; Membrane Transport Proteins; Molecular Sequence Data; Oligopeptides; Peptide Library; Peptides
PubMed: 9843435
DOI: 10.1021/bi981712t -
Pflugers Archiv : European Journal of... May 2009Movement of urea across plasma membranes is modulated by specialized urea transporter proteins. Two urea-transporter genes have been cloned: UT-A (Slc14a2) and UT-B... (Review)
Review
Movement of urea across plasma membranes is modulated by specialized urea transporter proteins. Two urea-transporter genes have been cloned: UT-A (Slc14a2) and UT-B (Slc14a1). In the mammalian kidney, urea transporters are essential for the urinary concentrating mechanism and maintaining body fluid homeostasis. In this article, we discuss (1) an overview of historic discoveries in urea transport mechanisms; (2) an overview of recent discoveries in the regulation of urea transporters; (3) physiological studies in UT-A1/3 (-/-) mice highlighting the essential role of urea transporters in the urinary concentrating mechanism; and (4) physiological studies in UT-A2 and UT-B knockout mice examining the role of countercurrent exchange in the production of a maximally concentrated urine.
Topics: Animals; Arginine Vasopressin; Biological Transport; Glomerular Filtration Rate; Kidney; Kidney Medulla; Membrane Transport Proteins; Mice; Mice, Knockout; Phosphorylation; Receptors, Vasopressin; Ubiquitination; Urea; Vasopressins; Urea Transporters
PubMed: 19011892
DOI: 10.1007/s00424-008-0612-4 -
Molecular and Cellular Endocrinology Feb 2010Peptide transport and expression of SoLute Carrier 15 (SLC15) peptide transporters was assessed in rat thyroid tissue and a rat thyroid cell line (PC Cl3 cells). Peptide...
Peptide transport and expression of SoLute Carrier 15 (SLC15) peptide transporters was assessed in rat thyroid tissue and a rat thyroid cell line (PC Cl3 cells). Peptide transport was studied by monitoring the uptake of the fluorophore-conjugated dipeptide beta-Ala-Lys-N(epsilon)-7-amino-4-methyl-coumarin-3-acetic acid (Ala-Lys-AMCA). Expression of SLC15-specific mRNA transcripts was analyzed by RT-PCR. Of the two SLC15 transporters expressed in thyroid follicular cells, namely PEPT2 (SLC15A2) and PHT1 (SLC15A4), only PEPT2 was involved in peptide transport at the plasma membrane, with PHT1 most likely being intracellular. Interestingly, at the mRNA level PEPT2 was up-regulated under TSH stimulation. These findings represent the first evidence that peptide transport occurs in thyroid follicular cells. SLC15 transporters could participate to recycling of peptides derived from extracellular and lysosomal thyroglobulin proteolysis, both essential steps for thyroid hormone synthesis.
Topics: Animals; Cell Line; Dipeptides; Membrane Transport Proteins; Nerve Tissue Proteins; Peptide Transporter 1; Protein Isoforms; RNA, Messenger; Rats; Rats, Sprague-Dawley; Symporters; Thyroid Gland; Thyrotropin
PubMed: 19913073
DOI: 10.1016/j.mce.2009.11.002 -
Scientific Reports Jul 2020Lanthipeptides are ribosomally synthesized and post-translationally modified peptides containing dehydrated amino acids and (methyl-)lanthionine rings. One of the...
Lanthipeptides are ribosomally synthesized and post-translationally modified peptides containing dehydrated amino acids and (methyl-)lanthionine rings. One of the best-studied examples is nisin produced by Lactococcus lactis. Nisin is synthesized as a precursor peptide comprising of an N-terminal leader peptide and a C-terminal core peptide. Amongst others, the leader peptide is crucial for enzyme recognition and acts as a secretion signal for the ABC transporter NisT that secretes nisin in a proposed channeling mechanism. Here, we present an in vivo secretion analysis of this process in the presence and absence of the nisin maturation machinery, consisting of the dehydratase NisB and the cyclase NisC. Our determined apparent secretion rates of NisT show how NisB and NisC modulate the transport kinetics of NisA. Additional in vitro studies of the detergent-solubilized NisT revealed how these enzymes and the substrates again influence the activity of transporter. In summary, this study highlights the pivotal role of NisB for NisT in the secretion process.
Topics: Bacterial Proteins; Enzyme Activation; Gene Order; Membrane Transport Proteins; Nisin; Protein Binding; Protein Transport
PubMed: 32703992
DOI: 10.1038/s41598-020-69225-2 -
Drug Metabolism and Pharmacokinetics Dec 2007Many types of xenobiotic transporters have been identified. They generally exhibit multispecific recognition of various types of substrates, and mediate membrane... (Review)
Review
Many types of xenobiotic transporters have been identified. They generally exhibit multispecific recognition of various types of substrates, and mediate membrane permeation of therapeutic agents, thereby playing important roles in drug absorption and disposition. It has recently been proposed that protein-protein interactions involving the xenobiotic transporters may affect their function, localization and expression on plasma membranes. So-called adaptor proteins that directly interact with the transporters include PDZ domain-containing proteins (PSD95, Dlg and ZO1). These PDZ adaptors have multiple PDZ domains in their structure, and each PDZ domain can interact with the cytosolic region of the transporters, and so it has been hypothesized that transporters are localized within networks consisting of several transporters and adaptors. Interaction with a PDZ adaptor is essential for the cell-surface localization of at least some xenobiotic transporters, and therefore, such interaction could be required for efficiency and fidelity in the vectorial transport of xenobiotics and therapeutic agents in epithelial cells. This review article summarizes recent evidence on the interactions of xenobiotic transporters with adaptor proteins, and presents a working hypothesis concerning their pharmacological significance.
Topics: Adaptor Proteins, Signal Transducing; Animals; Binding Sites; Biological Transport; Cell Membrane; Humans; Membrane Transport Proteins; PDZ Domains; Pharmacokinetics; Protein Binding; Protein Conformation; Xenobiotics
PubMed: 18159127
DOI: 10.2133/dmpk.22.401 -
Yakugaku Zasshi : Journal of the... 2021The blood-brain barrier (BBB) consists of brain capillary endothelial cells linked by tight junctions and serves to regulate the transfer of endogenous compounds and... (Review)
Review
The blood-brain barrier (BBB) consists of brain capillary endothelial cells linked by tight junctions and serves to regulate the transfer of endogenous compounds and xenobiotics between the circulating blood and brain interstitial fluid. We have developed a methodology to characterize brain-to-blood efflux transport in vivo, using the Brain Efflux Index and an in vitro culture model of the BBB, i.e., a conditionally immortalized cell line of the neurovascular unit. Employing these methods, we showed that the BBB plays an important role in protecting the brain by transporting neurotransmitters, neuromodulators, metabolites, uremic toxins, and xenobiotics together with atrial natriuretic peptide from the brain interstitial fluid to the circulating blood. We also developed a highly selective, sensitive LC-MS/MS method for simultaneous protein quantification. We found significant species differences in the expression amounts of various BBB transporter proteins among mice, rats, marmosets, cynomolgus monkeys, and humans. Among transporter proteins at the BBB, multidrug resistance protein 1 (Mdr1/Abcb1) is known to generate a concentration gradient of unbound substrate drugs between the blood and brain. Based on measurements of the intrinsic efflux transport rate of Mdr1 and the protein expression amounts of Mdr1 in mouse brain capillaries and Mdr1-expressing cell lines, we predicted the unbound drug concentration gradients of 7 drugs in the mouse brain in vivo. This was the first successful prediction of in vivo drug transport activity from in vitro experimental data and transporter protein concentration in tissues. This methodology and findings should greatly advance central nervous system barrier research.
Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Animals; Biological Transport; Blood-Brain Barrier; Brain; Cell Line; Chromatography, Liquid; Humans; Membrane Transport Proteins; Mice; Neurotransmitter Agents; Proteomics; Rats; Tandem Mass Spectrometry; Xenobiotics
PubMed: 33790111
DOI: 10.1248/yakushi.20-00232 -
Eukaryotic Cell Apr 2013Fungi possess two distinct proton-coupled peptide transport systems, the dipeptide/tripeptide transporters (PTR) and the oligopeptide transporters (OPT), which enable...
Fungi possess two distinct proton-coupled peptide transport systems, the dipeptide/tripeptide transporters (PTR) and the oligopeptide transporters (OPT), which enable them to utilize peptides as nutrients. In the pathogenic yeast Candida albicans, peptide transporters are encoded by gene families consisting of two PTR genes and eight OPT genes. To gain insight into the functions and importance of specific peptide transporters, we generated mutants lacking the two dipeptide/tripeptide transporters Ptr2 and Ptr22, as well as the five major oligopeptide transporters Opt1 to Opt5. These mutants were unable to grow in media containing peptides as the sole nitrogen source. Forced expression of individual peptide transporters in the septuple mutants showed that Ptr2 and Ptr22 could utilize all tested dipeptides as substrates but differed in their abilities to transport specific tripeptides. Interestingly, several oligopeptide transporters, which are thought to transport peptides consisting of more than three amino acids, also mediated the uptake of tripeptides. Opt1 especially turned out to be a highly flexible transporter that enabled growth on all tripeptides tested and could even utilize a dipeptide, a function that has never been ascribed to this family of peptide transporters. Despite their inability to grow on proteins or peptides, the opt1Δ opt2Δ opt3Δ opt4Δ opt5Δ ptr2Δ ptr22Δ septuple mutants had no in vivo fitness defect in a mouse model of gastrointestinal colonization. Therefore, the nutritional versatility of C. albicans enables it to utilize alternative nitrogen sources in this host niche, which probably contributes to its success as a commensal and pathogen in mammalian hosts.
Topics: Amino Acids; Animals; Candida albicans; Candidiasis; Dipeptides; Female; Fungal Proteins; Gene Expression Regulation, Fungal; Genetic Complementation Test; Membrane Transport Proteins; Mice; Mice, Inbred BALB C; Monosaccharide Transport Proteins; Mutation; Protein Transport; Substrate Specificity
PubMed: 23376942
DOI: 10.1128/EC.00008-13 -
Metabolic Engineering Jan 2017Semipermeable membranes of cells frequently pose an obstacle in metabolic engineering by limiting uptake of substrates, intermediates, or xenobiotics. Previous attempts...
Semipermeable membranes of cells frequently pose an obstacle in metabolic engineering by limiting uptake of substrates, intermediates, or xenobiotics. Previous attempts to overcome this barrier relied on the promiscuous nature of peptide transport systems, but often suffered from low versatility or chemical instability. Here, we present an alternative strategy to transport cargo molecules across the inner membrane of Escherichia coli based on chemical synthesis of a stable cargo-peptide vector construct, transport through the peptide import system, and efficient intracellular release of the cargo by the promiscuous enzyme γ-glutamyl transferase (GGT). Retaining the otherwise periplasmic GGT in the cytoplasm was critical for the functionality of the system, as was fine-tuning its expression in order to minimize toxic effects associated to cytoplasmic GGT expression. Given the established protocols of peptide synthesis and the flexibility of peptide transport and GGT, the system is expected to be suitable for a broad range of cargoes.
Topics: Biological Transport, Active; Biosynthetic Pathways; Cell Membrane; Cell Membrane Permeability; Escherichia coli; Genetic Enhancement; Intracellular Fluid; Membrane Transport Proteins; Metabolic Engineering; Metabolic Networks and Pathways; Peptides; gamma-Glutamyltransferase
PubMed: 27989807
DOI: 10.1016/j.ymben.2016.10.016