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Scientific Reports May 2021ATP binding cassette (ABC) transporters employ ATP hydrolysis to harness substrate translocation across membranes. The Escherichia coli MalFGKE maltose importer is an...
ATP binding cassette (ABC) transporters employ ATP hydrolysis to harness substrate translocation across membranes. The Escherichia coli MalFGKE maltose importer is an example of a type I ABC importer and a model system for this class of ABC transporters. The MalFGKE importer is responsible for the intake of malto-oligossacharides in E.coli. Despite being extensively studied, little is known about the effect of ATP hydrolysis and nucleotide exit on substrate transport. In this work, we studied this phenomenon using extensive molecular dynamics simulations (MD) along with potential of mean force calculations of maltose transport across the pore, in the pre-hydrolysis, post-hydrolysis and nucleotide-free states. We concluded that ATP hydrolysis and nucleotide exit trigger conformational changes that result in the decrease of energetic barriers to maltose translocation towards the cytoplasm, with a concomitant increase of the energy barrier in the periplasmic side of the pore, contributing for the irreversibility of the process. We also identified key residues that aid in positioning and orientation of maltose, as well as a novel binding pocket for maltose in MalG. Additionally, ATP hydrolysis leads to conformations similar to the nucleotide-free state. This study shows the contribution of ATP hydrolysis and nucleotide exit in the transport cycle, shedding light on ABC type I importer mechanisms.
Topics: ATP-Binding Cassette Transporters; Adenosine Triphosphate; Escherichia coli; Escherichia coli Proteins; Hydrolysis; Maltose; Protein Conformation
PubMed: 34012037
DOI: 10.1038/s41598-021-89556-y -
Microbiology and Molecular Biology... Mar 1998The maltose system of Escherichia coli offers an unusually rich set of enzymes, transporters, and regulators as objects of study. This system is responsible for the... (Review)
Review
The maltose system of Escherichia coli offers an unusually rich set of enzymes, transporters, and regulators as objects of study. This system is responsible for the uptake and metabolism of glucose polymers (maltodextrins), which must be a preferred class of nutrients for E. coli in both mammalian hosts and in the environment. Because the metabolism of glucose polymers must be coordinated with both the anabolic and catabolic uses of glucose and glycogen, an intricate set of regulatory mechanisms controls the expression of mal genes, the activity of the maltose transporter, and the activities of the maltose/maltodextrin catabolic enzymes. The ease of isolating many of the mal gene products has contributed greatly to the understanding of the structures and functions of several classes of proteins. Not only was the outer membrane maltoporin, LamB, or the phage lambda receptor, the first virus receptor to be isolated, but also its three-dimensional structure, together with extensive knowledge of functional sites for ligand binding as well as for phage lambda binding, has led to a relatively complete description of this sugar-specific aqueous channel. The periplasmic maltose binding protein (MBP) has been studied with respect to its role in both maltose transport and maltose taxis. Again, the combination of structural and functional information has led to a significant understanding of how this soluble receptor participates in signaling the presence of sugar to the chemosensory apparatus as well as how it participates in sugar transport. The maltose transporter belongs to the ATP binding cassette family, and although its structure is not yet known at atomic resolution, there is some insight into the structures of several functional sites, including those that are involved in interactions with MBP and recognition of substrates and ATP. A particularly astonishing discovery is the direct participation of the transporter in transcriptional control of the mal regulon. The MalT protein activates transcription at all mal promoters. A subset also requires the cyclic AMP receptor protein for transcription. The MalT protein requires maltotriose and ATP as ligands for binding to a dodecanucleotide MalT box that appears in multiple copies upstream of all mal promoters. Recent data indicate that the ATP binding cassette transporter subunit MalK can directly inhibit MalT when the transporter is inactive due to the absence of substrate. Despite this wealth of knowledge, there are still basic issues that require clarification concerning the mechanism of MalT-mediated activation, repression by the transporter, biosynthesis and assembly of the outer membrane and inner membrane transporter proteins, and interrelationships between the mal enzymes and those of glucose and glycogen metabolism.
Topics: Amino Acid Sequence; Base Sequence; Biological Transport; Escherichia coli; Genes, Bacterial; Maltose; Molecular Sequence Data; Polysaccharides
PubMed: 9529892
DOI: 10.1128/MMBR.62.1.204-229.1998 -
International Journal of Molecular... May 2022Microorganisms often live in complex habitats, where changes in the environment are predictable, providing an opportunity for microorganisms to learn, anticipate the...
Microorganisms often live in complex habitats, where changes in the environment are predictable, providing an opportunity for microorganisms to learn, anticipate the upcoming environmental changes and prepare in advance for better survival and growth. One such environment is the mammalian intestine, where the abundance of different carbon sources is spatially distributed. In this study, we identified seven spatially distributed carbon sources in the mammalian intestine and tested whether exhibits phenotypes that are consistent with an anticipatory response given their spatial order and abundance within the mammalian intestine. Through RNA-Seq and RT-PCR validation measurements, we found that there was a 67% match in the expression patterns between the measured phenotypes and what would otherwise be expected in the case of anticipatory behavior, while 83% and 0% were in agreement with the homeostatic and random response, respectively. To understand the genetic and phenotypic basis of the discrepancies between the expected and measured anticipatory responses, we thoroughly investigated the discrepancy in D-galactose treatment and the expression of maltose operon in . Here, the expected anticipatory response, based on the spatial distribution of D-galactose and D-maltose, was that D-galactose should upregulate the maltose operon, but it was the opposite in experimental validation. We performed whole genome random mutagenesis and screening and identified strains with positive expression of maltose operon in D-galactose. Targeted Sanger sequencing and mutation repair identified that the mutations in the promoter region of and in the coding region of the gene were the factors responsible for the reversion in the association. Further, to identify why positive association in the D-galactose treatment and the expression of the maltose operon did not evolve naturally, fitness measurements were performed. Fitness experiments demonstrated that the fitness of strains with a positive association in the D-galactose treatment and the expression of the maltose operon was 12% to 20% lower than that of the wild type strain.
Topics: Carbon; Escherichia coli; Galactose; Maltose; Mutation; Operon
PubMed: 35682665
DOI: 10.3390/ijms23115985 -
Applied Microbiology and Biotechnology May 2021In a competitive microbial environment, nutrient acquisition is a major contributor to the survival of any individual bacterial species, and the ability to access... (Review)
Review
In a competitive microbial environment, nutrient acquisition is a major contributor to the survival of any individual bacterial species, and the ability to access uncommon energy sources can provide a fitness advantage. One set of soluble carbohydrates that have attracted increased attention for use in biotechnology and biomedicine is the α-diglucosides. Maltose is the most well-studied member of this class; however, the remaining four less common α-diglucosides (trehalose, kojibiose, nigerose, and isomaltose) are increasingly used in processed food and fermented beverages. The consumption of trehalose has recently been shown to be a contributing factor in gut microbiome disease as certain pathogens are using α-diglucosides to outcompete native gut flora. Kojibiose and nigerose have also been examined as potential prebiotics and alternative sweeteners for a variety of foods. Compared to the study of maltose metabolism, our understanding of the synthesis and degradation of uncommon α-diglucosides is lacking, and several fundamental questions remain unanswered, particularly with regard to the regulation of bacterial metabolism for α-diglucosides. Therefore, this minireview attempts to provide a focused analysis of uncommon α-diglucoside metabolism in bacteria and suggests some future directions for this research area that could potentially accelerate biotechnology and biomedicine developments. KEY POINTS: • α-diglucosides are increasingly important but understudied bacterial metabolites. • Kinetically superior α-diglucoside enzymes require few amino acid substitutions. • In vivo studies are required to realize the biotechnology potential of α-diglucosides.
Topics: Bacteria; Biotechnology; Isomaltose; Maltose; Trehalose
PubMed: 33961116
DOI: 10.1007/s00253-021-11322-x -
Research in Microbiology Sep 2002Seeing connections between apparently unrelated areas is the hallmark of a deep thinker. Maurice Hofnung showed that his interest in the maltose regulon and my own... (Review)
Review
Seeing connections between apparently unrelated areas is the hallmark of a deep thinker. Maurice Hofnung showed that his interest in the maltose regulon and my own interest in the regulation of cell division in Escherichia coli could lead to fruitful collaboration. From the maltose regulon to the LamB receptor to phage A to the SOS response to the Mutatest to induction of expression of the SOS-inducible division inhibitor SfiA to the SOS Chromotest based on sfiA::lacZ induction to the development of a commercial kit for measuring the genotoxicity of environmental substances...this was but one of the original trails that Maurice Hofnung blazed and exploited successfully.
Topics: Cell Division; Colorimetry; Escherichia coli; History, 20th Century; Maltose; Mutagenicity Tests; SOS Response, Genetics
PubMed: 12405348
DOI: 10.1016/s0923-2508(02)01341-4 -
European Journal of Pediatrics Nov 2022Iron deficiency is the primary cause of anaemia worldwide and is particularly common among children and adolescents. Intravenous (IV) iron therapy is recommended for... (Review)
Review
UNLABELLED
Iron deficiency is the primary cause of anaemia worldwide and is particularly common among children and adolescents. Intravenous (IV) iron therapy is recommended for paediatric patients with certain comorbidities or if oral iron treatment has been unsuccessful. IV ferric carboxymaltose (FCM) has recently been approved by the US Food and Drug Administration for use in children aged > 1 year. This narrative review provides an overview of the available publications on the efficacy and safety of IV FCM in children and adolescents. A literature search using PubMed and Embase yielded 153 publications; 33 contained clinical data or reports on clinical experience relating to IV FCM in subjects < 18 years of age and were included in the review. No prospective, randomised controlled studies on the topic were found. Most publications were retrospective studies or case reports and included patients with various underlying conditions or patients with inflammatory bowel disease. Efficacy data were included in 27/33 publications and improvements in anaemia, and/or iron status parameters were reported in 26 of them. Safety data were included in 25/33 publications and were in line with the adverse events described in the prescribing information.
CONCLUSION
The available publications indicate that IV FCM, a nanomedicine with a unique and distinctive therapeutic profile, is an effective and generally well-tolerated treatment for iron deficiency or iron deficiency anaemia in children and adolescents. Despite the wealth of retrospective evidence, prospective, randomised controlled trials in the paediatric setting are still necessary.
WHAT IS KNOWN
• Iron deficiency and iron deficiency anaemia are usually managed using oral iron therapy, but intravenous iron therapy is recommended for certain paediatric patients. • Intravenous ferric carboxymaltose (FCM) has recently been approved in the US for use in children aged > 1 year.
WHAT IS NEW
• Despite evidence that FCM is effective and generally well tolerated in children and adolescents, so far, only retrospective studies, non-randomised uncontrolled prospective studies, or case reports have been published in full. • There is a strong need for prospective, randomised controlled trials on FCM in the paediatric setting.
Topics: Administration, Intravenous; Adolescent; Anemia, Iron-Deficiency; Child; Ferric Compounds; Humans; Iron; Iron Deficiencies; Maltose; Prospective Studies; Retrospective Studies; Treatment Outcome
PubMed: 36056175
DOI: 10.1007/s00431-022-04582-w -
Molecular & Cellular Proteomics : MCP Sep 2015The goal of next-level bottom-up membrane proteomics is protein function investigation, via high-coverage high-throughput peptide-centric quantitation of expression,... (Review)
Review
The goal of next-level bottom-up membrane proteomics is protein function investigation, via high-coverage high-throughput peptide-centric quantitation of expression, modifications and dynamic structures at systems scale. Yet efficient digestion of mammalian membrane proteins presents a daunting barrier, and prevalent day-long urea-trypsin in-solution digestion proved insufficient to reach this goal. Many efforts contributed incremental advances over past years, but involved protein denaturation that disconnected measurement from functional states. Beyond denaturation, the recent discovery of structure/proteomics omni-compatible detergent n-dodecyl-β-d-maltopyranoside, combined with pepsin and PNGase F columns, enabled breakthroughs in membrane protein digestion: a 2010 DDM-low-TCEP (DLT) method for H/D-exchange (HDX) using human G protein-coupled receptor, and a 2015 flow/detergent-facilitated protease and de-PTM digestions (FDD) for integrative deep sequencing and quantitation using full-length human ion channel complex. Distinguishing protein solubilization from denaturation, protease digestion reliability from theoretical specificity, and reduction from alkylation, these methods shifted day(s)-long paradigms into minutes, and afforded fully automatable (HDX)-protein-peptide-(tandem mass tag)-HPLC pipelines to instantly measure functional proteins at deep coverage, high peptide reproducibility, low artifacts and minimal leakage. Promoting-not destroying-structures and activities harnessed membrane proteins for the next-level streamlined functional proteomics. This review analyzes recent advances in membrane protein digestion methods and highlights critical discoveries for future proteomics.
Topics: Animals; Humans; Maltose; Membrane Proteins; Proteolysis; Proteomics; Reproducibility of Results; Tandem Mass Spectrometry; Trypsin; Urea
PubMed: 26081834
DOI: 10.1074/mcp.R114.042572 -
Scientific Reports Mar 2017Mammalian cells are generally considered to be unable to utilize polysaccharides for cell growth because the phospholipid bilayer in the cell membrane has very low...
Mammalian cells are generally considered to be unable to utilize polysaccharides for cell growth because the phospholipid bilayer in the cell membrane has very low permeability to sugars. With the recent discovery of the only known animal disaccharide transporter, a sucrose transporter, we considered the potential use of polysaccharides as energy source, because that can impact biopharmaceutical manufacturing by potentially increasing carbohydrate loading in the culture medium and decreasing lactate accumulation. In this study, we found that mammalian cells can utilize maltose for growth in the absence of glucose and successfully adapted CHO-K1, CHO-DG44 and HEK293 cells to grow in glucose-free, maltose-containing serum-free protein-free media. We then cultivated a non-adapted CHO-K1 producer cell line in media containing both glucose and maltose to show that the cells can utilize maltose in a biphasic manner, that maltose enters the cells, and that maltose utilization only took place in the presence of the cells. This is the first report of a protein-free mammalian cell culture using a disaccharide as energy source.
Topics: Animals; CHO Cells; Cell Culture Techniques; Cricetinae; Cricetulus; Culture Media, Serum-Free; Glucose; HEK293 Cells; Humans; Maltose
PubMed: 28358044
DOI: 10.1038/srep45216 -
Molecular Microbiology Aug 1998Bacterial ATP-binding cassette (ABC) transporters and their homologues in eukaryotic cells form one of the largest superfamilies known today. They function as primary... (Review)
Review
Bacterial ATP-binding cassette (ABC) transporters and their homologues in eukaryotic cells form one of the largest superfamilies known today. They function as primary pumps that couple substrate translocation across the cytoplasmic membrane to ATP hydrolysis. Although ABC transporters have been studied for more than three decades, the structure of these multi-component systems is unknown, and the mechanism of transport is not understood. This article reviews one of the most widely studied ABC systems, the maltose transporter of Escherichia coli. A first structural model of the transport channel allows discussion of possible mechanisms of transport. In addition, recent experimental evidence suggests that regulation of gene expression and transport activity is far more complex than expected.
Topics: ATP-Binding Cassette Transporters; Adenosine Triphosphatases; Animals; Biological Transport; Cell Membrane; Humans; Maltose; Models, Biological
PubMed: 9723909
DOI: 10.1046/j.1365-2958.1998.00915.x -
European Journal of Clinical... Nov 2021Over the last years, several trials offered new evidence on heart failure (HF) treatment. (Review)
Review
BACKGROUND
Over the last years, several trials offered new evidence on heart failure (HF) treatment.
DESIGN AND RESULTS
For HF with reduced left ventricular ejection fraction, type 2 sodium-glucose cotransporter inhibitors, aside from sacubitril-valsartan, demonstrated extraordinary efficacy in ameliorating patients' prognosis. Some new molecules (eg vericiguat, omecamtiv mecarbil and ferric carboxymaltose) correct iron deficiency and have shown to be capable of furthering reducing the burden of HF hospitalisation. Finally, there is new evidence on the possible therapeutic approaches of HF patients with mid-range or preserved left ventricular ejection fraction.
CONCLUSIONS
This review aimed to revise the main novelties in the field of HF therapy and focus on how the daily clinical approach to patient treatment is changing.
Topics: Aminobutyrates; Angiotensin Receptor Antagonists; Biphenyl Compounds; Cardiotonic Agents; Drug Combinations; Ferric Compounds; Heart Failure; Heterocyclic Compounds, 2-Ring; Hospitalization; Humans; Iron Deficiencies; Maltose; Pyrimidines; Sodium-Glucose Transporter 2 Inhibitors; Stroke Volume; Urea; Valsartan; Vasodilator Agents; Ventricular Remodeling
PubMed: 34043809
DOI: 10.1111/eci.13624