Molecular characterization of substrate-binding sites in the glutamate transporter family

2001 ◽  
Vol 29 (6) ◽  
pp. 707-710 ◽  
Author(s):  
B. I. Kanner ◽  
M. P. Kavanaugh ◽  
A. Bendahan
Keyword(s):  
Glutamate Transporter ◽  
Glutamate Transporters ◽  
Amino Acid Residues ◽  
Sodium Potassium ◽  
Synaptic Excitation ◽  
Transporter Family ◽  
Carboxyl Terminal ◽  
Substrate Binding Sites

Glutamate transporters are essential for terminating synaptic excitation and for maintaining extracellular glutamate concentrations below neurotoxic levels. These transporters also mediate a thermodynamically uncoupled chloride flux that is activated by two of the molecules that they transport – sodium and glutamate. Five eukaryotic glutamate transporters have been cloned and identified. They exhibit ~ 50% identity and this homology is even greater in the carboxyl terminal half, which is predicted to have an unusual topology. Determination of the topology shows that the carboxyl terminal part of the molecule contains several transmembrane domains that are separated by at least two re-entrant loops. In these structural elements, we have identified several conserved amino acid residues that play crucial roles in the interaction with the transporter substrates sodium, potassium and glutamate.

scholarly journals Mechanisms of Glutamate Transport

2013 ◽  
Vol 93 (4) ◽  
pp. 1621-1657 ◽  
Author(s):  
Robert J. Vandenberg ◽  
Renae M. Ryan
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Glutamate Transporter ◽  
Glutamate Transporters ◽  
Structural Basis ◽  
Broad Perspective ◽  
Excitatory Neurotransmitter ◽  
Brain Functions ◽  
Transporter Family ◽  
The Central Nervous System

l-Glutamate is the predominant excitatory neurotransmitter in the mammalian central nervous system and plays important roles in a wide variety of brain functions, but it is also a key player in the pathogenesis of many neurological disorders. The control of glutamate concentrations is critical to the normal functioning of the central nervous system, and in this review we discuss how glutamate transporters regulate glutamate concentrations to maintain dynamic signaling mechanisms between neurons. In 2004, the crystal structure of a prokaryotic homolog of the mammalian glutamate transporter family of proteins was crystallized and its structure determined. This has paved the way for a better understanding of the structural basis for glutamate transporter function. In this review we provide a broad perspective of this field of research, but focus primarily on the more recent studies with a particular emphasis on how our understanding of the structure of glutamate transporters has generated new insights.

Characterization of the major form of cholecystokinin in human intestine: CCK-58

1990 ◽  
Vol 258 (2) ◽  
pp. G253-G260 ◽  
Author(s):  
V. E. Eysselein ◽  
G. A. Eberlein ◽  
M. Schaeffer ◽  
D. Grandt ◽  
H. Goebell ◽  
...  
Keyword(s):  
High Pressure ◽  
Cross Reactivity ◽  
Organ Donors ◽  
Human Intestine ◽  
Reverse Phase Hplc ◽  
Reverse Phase ◽  
Carboxyl Terminal ◽  
Circulating Levels

Acid extracts of human intestines obtained from surgical samples or from organ donors contain cholecystokinin (CCK) immunoreactivity. From surgical samples, extracted and eluted quickly, greater than 75% of the CCK immunoreactivity eluted in the same region as purified canine CCK-58 during analytical reverse-phase high-pressure liquid chromatography (HPLC). A major portion of the CCK immunoreactivity from donor intestinal extracts also eluted in this region. This immunoreactivity has been purified from human intestinal extracts by a series of several reverse-phase and cation-exchange chromatographies. Amino acid and microsequence analysis showed that this immunoreactivity is human CCK-58. Tryptic digestion of purified human CCK-58 produced another immunoreactive form that eluted in the position of CCK-8 during analytical reverse-phase HPLC. The immunoreactivity of the trypsin-digested material was 2.6-fold higher than that of an identical sample of CCK-58 incubated without trypsin. Thus the carboxyl-terminal antibody used for radioimmunoassay cross-reacts greater than twofold less with human CCK-58. This diminished cross-reactivity would lead to an underestimation of the relative proportions of CCK-58 in tissue and plasma extracts. If CCK-58 is the major circulating form this diminished cross-reactivity would also lead to underestimations of the circulating levels of total CCK. Determination of human CCK-58 structure confirms that one of the major components of human CCK that expresses biological activity is CCK-58.

scholarly journals Structural Features of the Glutamate Transporter Family

1999 ◽  
Vol 63 (2) ◽  
pp. 293-307 ◽  
Author(s):  
Dirk Jan Slotboom ◽  
Wil N. Konings ◽  
Juke S. Lolkema
Keyword(s):  
Amino Acid ◽  
Glutamate Transporter ◽  
Glutamate Transporters ◽  
Amino Acid Sequences ◽  
Neutral Amino Acid ◽  
Amino Acid Transporters ◽  
Conserved Sequence ◽  
Transporter Family ◽  
The Family ◽  
Membrane Spanning

SUMMARY Neuronal and glial glutamate transporters remove the excitatory neurotransmitter glutamate from the synaptic cleft and thus prevent neurotoxicity. The proteins belong to a large and widespread family of secondary transporters, including bacterial glutamate, serine, and C4-dicarboxylate transporters; mammalian neutral-amino-acid transporters; and an increasing number of bacterial, archaeal, and eukaryotic proteins that have not yet been functionally characterized. Sixty members of the glutamate transporter family were found in the databases on the basis of sequence homology. The amino acid sequences of the carriers have diverged enormously. Homology between the members of the family is most apparent in a stretch of approximately 150 residues in the C-terminal part of the proteins. This region contains four reasonably well-conserved sequence motifs, all of which have been suggested to be part of the translocation pore or substrate binding site. Phylogenetic analysis of the C-terminal stretch revealed the presence of five subfamilies with characterized members: (i) the eukaryotic glutamate transporters, (ii) the bacterial glutamate transporters, (iii) the eukaryotic neutral-amino-acid transporters, (iv) the bacterial C4-dicarboxylate transporters, and (v) the bacterial serine transporters. A number of other subfamilies that do not contain characterized members have been defined. In contrast to their amino acid sequences, the hydropathy profiles of the members of the family are extremely well conserved. Analysis of the hydropathy profiles has suggested that the glutamate transporters have a global structure that is unique among secondary transporters. Experimentally, the unique structure of the transporters was recently confirmed by membrane topology studies. Although there is still controversy about part of the topology, the most likely model predicts the presence of eight membrane-spanning α-helices and a loop-pore structure which is unique among secondary transporters but may resemble loop-pores found in ion channels. A second distinctive structural feature is the presence of a highly amphipathic membrane-spanning helix that provides a hydrophilic path through the membrane. Recent data from analysis of site-directed mutants and studies on the mechanism and pharmacology of the transporters are discussed in relation to the structural model.

scholarly journals Characterization of Ubiquitin Carboxyl-Terminal Hydrolase L1 (UCH-L1) in the Fate Determination of Spermatogonia.

2010 ◽  
Vol 83 (Suppl_1) ◽  
pp. 388-388
Author(s):  
Lin Tang ◽  
Marie-Claude C. Hofmann ◽  
Ina Dobrinski
Keyword(s):  
Fate Determination ◽  
Carboxyl Terminal

scholarly journals Glutamate transporters contain a conserved chloride channel with two hydrophobic gates

2020 ◽  
Author(s):  
Ichia Chen ◽  
Shashank Pant ◽  
Qianyi Wu ◽  
Rosemary Cater ◽  
Meghna Sobti ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Glutamate Transporter ◽  
Glutamate Transporters ◽  
Chloride Ions ◽  
Dual Function ◽  
Normal Brain ◽  
Ph Gradients ◽  
Excitatory Neurotransmitter ◽  
Transporter Family ◽  
Transport Cycle

AbstractGlutamate is the most abundant excitatory neurotransmitter in the central nervous system, therefore its precise control is vital for maintaining normal brain function and preventing excitotoxicity1. Removal of extracellular glutamate is achieved by plasma membrane-bound transporters, which couple glutamate transport to sodium, potassium and pH gradients using an elevator mechanism2–5. Glutamate transporters also conduct chloride ions via a channel-like process that is thermodynamically uncoupled from transport6–8. However, the molecular mechanisms that allow these dual-function transporters to carry out two seemingly contradictory roles are unknown. Here we report the cryo-electron microscopy structure of a glutamate transporter homologue in an open-channel state, revealing an aqueous cavity that is formed during the transport cycle. Using functional studies and molecular dynamics simulations, we show that this cavity is an aqueous-accessible chloride permeation pathway gated by two hydrophobic regions, and is conserved across mammalian and archaeal glutamate transporters. Our findings provide insight into the mechanism by which glutamate transporters support their dual function and add a crucial piece of information to aid mapping of the complete transport cycle shared by the SLC1A transporter family.

Characterization of Impressed Current Technique to Model Corrosion of Reinforcement in Concrete

2020 ◽  
Vol 11 (1) ◽  
pp. 93-99
Author(s):  
Abu Zakir Morshed ◽  
Sheikh Shakib ◽  
Tanzim Jahin
Keyword(s):  
Immersion Time ◽  
Chloride Content ◽  
Engineering Science ◽  
Coastal Regions ◽  
Faraday’S Law ◽  
Current Technique ◽  
Corrosion Cell ◽  
Impressed Current

Corrosion of reinforcement is an important durability concern for the structures exposed to coastal regions. Since corrosion of reinforcement involves long periods of time, impressed current technique is usually used to accelerate the corrosion of reinforcement in laboratories. Characterization of impressed current technique was the main focus of this research,which involved determination of optimum chloride content and minimum immersion time of specimens for which the application of Faraday’s law could be efficient. To obtain optimum chloride content, the electrolytes in the corrosion cell were prepared similar to that of concrete pore solutions. Concrete prisms of 200 mm by 200 mm by 300 mm were used to determine the minimum immersion time for saturation. It was found that the optimum chloride content was 35 gm/L and the minimum immersion time for saturation was 140 hours. Accounting the results, a modified expression based on Faraday’s law was proposed to calculate weight loss due to corrosion. Journal of Engineering Science 11(1), 2020, 93-99

The Determination of Sense via Deleuze and Blanchot: Paradoxes of the Habitual, the Immemorial, and the Eternal Return

2008 ◽  
Vol 2 (2) ◽  
pp. 155-177 ◽  
Author(s):  
Eugene Brently Young
Keyword(s):  
Eternal Return

Eternal return is the paradox that accounts for the interplay between difference and repetition, a dynamic at the heart of Deleuze's philosophy, and Blanchot's approach to this paradox, even and especially through what it elides, further illuminates it. Deleuze draws on Blanchot's characterisations of difference, forgetting, and the unlivable to depict the ‘sense’ produced via eternal return, which, for Blanchot, is where repetition implicates or ‘carries’ pure difference. However, for Deleuze, difference and the unlivable are also developed by the living repetition or ‘contraction’ of habit, which results in his distinctive characterization of ‘force’, ‘levity’, and sense in eternal return.

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