Critical Roles of Two Hydrophobic Residues within Human Glucose Transporter 9 (hSLC2A9) in Substrate Selectivity and Urate Transport

Long, Wentong; Panwar, Pankaj; Witkowska, Kate; Wong, Kenneth; Oneill, D.M.; Chen, Xing-Zhen; Lemieux, M. Joanne; Cheeseman, Chris I.

doi:10.1074/jbc.m114.611178

Cited by 15 publications

(20 citation statements)

References 52 publications

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“…3E). As published previously, we have found a quasi-linear I-V relationship from −120 to 60 mV12, indicating that the membrane voltage mainly acts as a driving force for the urate transport (Fig. 3E).…”

Section: Resultssupporting

confidence: 86%

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Identification of Key Residues for Urate Specific Transport in Human Glucose Transporter 9 (hSLC2A9)

Long

Panigrahi

Panwar

et al. 2017

Sci Rep

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Human glucose transporter 9 (hSLC2A9) is critical in human urate homeostasis, for which very small deviations can lead to chronic or acute metabolic disorders. Human SLC2A9 is unique in that it transports hexoses as well as the organic anion, urate. This ability is in contrast to other homologous sugar transporters such as glucose transporters 1 and 5 (SLC2A1 & SLC2A5) and the xylose transporter (XylE), despite the fact that these transporters have similar protein structures. Our in silico substrate docking study has revealed that urate and fructose bind within the same binding pocket in hSLC2A9, yet with distinct orientations, and allowed us to identify novel residues for urate binding. Our functional studies confirmed that N429 is a key residue for both urate binding and transport. We have shown that cysteine residues, C181, C301 and C459 in hSLC2A9 are also essential elements for mediating urate transport. Additional data from chimæric protein analysis illustrated that transmembrane helix 7 of hSLC2A9 is necessary for urate transport but not sufficient to allow urate transport to be induced in glucose transporter 5 (hSLC2A5). These data indicate that urate transport in hSLC2A9 involves several structural elements rather than just a unique substrate binding pocket.

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Section: Resultssupporting

confidence: 86%

“…Substitution of isoleucine into valine in the fructose transporting hSLC2As only affects fructose but not glucose transport. This hydrophobic interaction also appears to have no effect on urate transport in hSLC2A91012. These findings also support the hypothesis that hexoses and urate have different binding residues in hSLC2A9.…”

supporting

confidence: 75%

Identification of Key Residues for Urate Specific Transport in Human Glucose Transporter 9 (hSLC2A9)

Long

Panigrahi

Panwar

et al. 2017

Sci Rep

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“…61 These models indicate that this hydrophobic residue (I335 in GLUT9 and I296 in GLUT5) is not projecting toward the aqueous transport pathway as previously proposed; instead, it appears to interact with residues on the adjacent TMs via an complex hydrophobic network (Figure 2). Additional functional studies confirmed that replacement of I335 in GLUT9 with valine resulted in a loss of trans-stimulation …”

Section: Importance Of Transmembrane Domain 7 In Glutsmentioning

confidence: 68%

“…60 However, analysis using a GLUT9 computer model based on the recent GLUT1 crystal structure indicates that this isoleucine is more likely to be facing away from the aqueous pore and to be acting as a structural regulator through hydrophobic interactions with adjacent TMs. 61 At the equivalent position in Class I GLUTs (except for GLUT2 which can also transport fructose) there is a valine residue. 7 This suggests that subtle interactions between TMs mediated by hydrophobic residues can affect substrate specificity within this family of transporters.…”

Section: Class II Glutsmentioning

confidence: 99%

Structure of, and functional insight into the GLUT family of membrane transporters

Long¹,

Cheeseman²

2015

CHC

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This review examines the development of structure and function of the human GLUT proteins, gene family hSLC2A. These proteins are essential for moving the key metabolites, glucose, galactose, and fructose in and out of cells, as well as a number of other important substrates. Despite over five decades of research, it is still not fully understood how they work at the molecular level, although the recent publication of a crystal structure of GLUT1 sug-

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“…In the uniporter research field, a much-studied phenomenon exists that is called trans-acceleration, 7 that is, the transport of one type of substrate (often radioisotope-labeled) from one side of the membrane can be accelerated by the existence of another type of substrate (e.g., unlabeled) on the opposite side of the membrane. In fact, this is one form of counter-flow experiment, although the two substrates on the opposite sides of the membrane may differ chemically (e.g., fructose vs. urate 11 ) or in concentration. In any of these experimental or natural processes, the inward transport is driven by the chemical potential of one substrate, whereas the outward transport is driven by the other, forming a functional cycle as a result.…”

Section: Kinetic Asymmetry Transacceleration and Othersmentioning

confidence: 99%

How does the chemical potential of the substrate drive a uniporter?

Zhang

Han

2016

Protein Science

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Uniporters are a large class of transporters mediating facilitated diffusion of substrates along the direction of the substrate concentration gradient. Recently, structures of several important uniporters have been reported; however, the precise mechanisms of uniporter function remain subject of debate. Here, we present a series of general thermodynamic descriptions of uniporters, aimed at understanding the structure-function relationship of uniporters, and in particular to reconcile biochemical phenomena of uniporters with our previously proposed thermodynamic model of general transporters.Keywords: uniporters; differential binding energy; elastic conformational energy; transition-state energy barrier; rate-limiting step; kinetic asymmetry UniporterThe cellular membrane presents a major energy barrier to hydrophilic small molecules to move across. This barrier is usually so high that translocation of these small molecules across the membrane along their concentration gradients is practically halted, even in the presence of a thermodynamically favorable chemical potential. The function of uniporters is to lower this energy barrier for selected substrates, so that the substrates can be transported along their own concentration gradients, a process called facilitated diffusion. A uniporter is a transporter that does not require energy input other than the substrate chemical potential. Like all transporters, a uniporter differs from a channel in that the former uses the alternating access mechanism 1 while the latter does not. Using this mechanism, a uniporter switches between two major conformations, namely inward-facing (C In ) and outwardfacing (C Out ), allowing its substrate-binding site to be accessible alternatingly to both sides of the membrane. The energy barrier for a hydrophilic molecule to transport passively across the cellular membrane is analogous to the transition-state energy barrier in a chemical reaction. According to the transitionstate theory of enzymology, an enzyme stabilizes the transition state of the reactants, thus effectively lowering the transition-state energy barrier. However, the reaction is driven by the chemical energy Abbreviations: C In , inward-facing conformation; C Out , outwardfacing conformation.

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Critical Roles of Two Hydrophobic Residues within Human Glucose Transporter 9 (hSLC2A9) in Substrate Selectivity and Urate Transport

Cited by 15 publications

References 52 publications

Identification of Key Residues for Urate Specific Transport in Human Glucose Transporter 9 (hSLC2A9)

Identification of Key Residues for Urate Specific Transport in Human Glucose Transporter 9 (hSLC2A9)

Structure of, and functional insight into the GLUT family of membrane transporters

How does the chemical potential of the substrate drive a uniporter?

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