Quantitative study of unsaturated transport of glycerol through aquaglyceroporin that has high affinity for glycerol

Rodríguez, R.; Chan, Ruth; Liang, Huiyun; Chen, L. Y.

doi:10.1039/d0ra05262k

Cited by 5 publications

(7 citation statements)

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“…AQPs are low molecular weight proteins, approximately 23-31 kDa, and their sequence-to-structure conservation is signi cant [4]. In addition to conducting water, AQPs are channels for small uncharged solutes such as CO 2 , H 2 O 2 , glycerol, NH 3 and urea, as well as metalloids such as silica, selenite, arsenite and boric acid [5][6][7][8][9][10]. Typical AQPs monomers consist of six transmembrane (TM) α-helices and two half-transmembrane α-helices, which are folded into monomers in an inverted front-backward manner.…”

Section: Introductionmentioning

confidence: 99%

“…The ar/R constriction, which comprises four amino acid residues, determines whether the channel is a strict water channel or a broadly selective solute channel bond and serves as the substrate screening region of the channel [5,[11][12][13]. As substrates enter the internal AQPs, favorable interactions between water and amino acid residues on the surface of the pore decrease, and solute-amino acid residue interactions take over; the stronger the interaction, the easier it is for the solute to pass through [10,14] .…”

Section: Introductionmentioning

confidence: 99%

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Characterization of SIPs-type aquaporins and their roles in response to environmental cues in rice (Oryza sativa L.)

Miao,

Shi,

Zheng

et al. 2023

Preprint

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Background Aquaporins (AQPs) facilitate water diffusion across biological membranes and are involved in all phases of growth and development. Small and basic intrinsic proteins (SIPs) belong to the fourth subfamily of the plant AQPs. Although SIPs are widely present in higher plants, reports on SIPs are limited. Rice is one of the major food crops in the world, and water use is an important factor affecting rice growth and development; therefore, this study aimed to provide information relevant to the function and environmental response of the rice SIP gene family. Results The rice (Oryza sativa L. japonica) genome encodes two SIP-like genes, OsSIP1 and OsSIP2, whose products are predominantly located in the endoplasmic reticulum (ER) membrane. Heterologous expression in a yeast aquaglyceroporin-mutant fps1Δ showed that both OsSIP1 and OsSIP2 made the cell more sensitive to KCl, sorbitol and H2O2, indicating facilitated permeation of water and hydrogen peroxide. In addition, the yeast cells expressing OsSIP2 were unable to efflux the toxic methylamine taken up by the endogenous MEP permeases, but OsSIP1 showed subtle permeability to methylamine, suggesting that OsSIP1 may have a wider conducting pore than OsSIP2. Expression profiling in different rice tissues or organs revealed that OsSIP1 was expressed in all tissues tested, whereas OsSIP2 was preferentially expressed in anthers and weakly expressed in other tissues. Consistent with this, histochemical staining of tissues expressing the promoter-β-glucuronidase fusion genes revealed their tissue-specific expression profile. In rice seedlings, both OsSIPs were more or less up-regulated under different stress conditions, including osmotic shock, high salinity, unfavorable temperature, redox challenge and pathogen attack, as well as by hormonal treatments such as GA, ABA, MeJA, SA. However, a reduced expression of both OsSIPs was observed under dehydration treatment. Conclusions OsSIP1 and OsSIP2 form the two-member Small Intrinsic Proteins subfamily of aquaporins in rice, they conduct water and H2O2. Moreover, OsSIP1 has a weak ability to conduct methylamine while OsSIP2 does not. Both proteins are mainly localized to the ER, although transient localization to the plasma membrane is not excluded. OsSIP1 is widely expressed in most tissues and during developmental stages, while OsSIP2 expressed preferentially in the anther. Both genes are up-regulated under a variety of stress conditions and by different hormone treatments, except that dehydration moderately reduces their expression. Our results pave the way for further deciphering the unique function of SIP-like aquaporins in substrate transport, growth and development, and environmental response in rice.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Characterization of SIPs-type aquaporins and their roles in response to environmental cues in rice (Oryza sativa L.)

Miao,

Shi,

Zheng

et al. 2023

Preprint

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“…If we insisted that unsaturated transport precludes high affinity, these experimental data would suggest inconsistency. However, in an in silico-in vitro study 16 of glycerol uptake into human erythrocytes through AQP3, 17 it was shown that an AQGP (having high affinity for its substrate glycerol) can conduct glycerol transport that is unsaturated up to 400 mM. The transport pathway for unsaturated transport through a high affinity facilitator protein was shown to involve two glycerol molecules next to each other both bound inside an AQP3 channel (one at the high affinity site and one at a low affinity site) for the transport of one glycerol molecule across the cell membrane.…”

Section: Introductionmentioning

confidence: 99%

“…The transport pathway for unsaturated transport through a high affinity facilitator protein was shown to involve two glycerol molecules next to each other both bound inside an AQP3 channel (one at the high affinity site and one at a low affinity site) for the transport of one glycerol molecule across the cell membrane. 16 It is the substrate-substrate interactions (mostly repulsion due to steric exclusion) inside a single-le channel that make it easy for two glycerol molecules cooperatively to move one substrate molecule across the AQGP channel via the high affinity site.…”

Section: Introductionmentioning

confidence: 99%

Aquaglyceroporin AQP7's affinity for its substrate glycerol. Have we reached convergence in the computed values of glycerol-aquaglyceroporin affinity?

2022

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“…However, in an in silico-in vitro study [16] of glycerol uptake into human erythrocytes through AQP3 [17], it was shown that an AQGP (having high affinity for its substrate glycerol) can conduct glycerol transport that is unsaturated up to 400 mM. The transport pathway for unsaturated transport through a high affinity facilitator protein was shown to involve two glycerol molecules next to each other both bound inside an AQP3 channel (one at the high affinity site and one at a low affinity site) for the transport of one glycerol molecule across the cell membrane [16]. It is the substrate-substrate interactions (mostly repulsion due to steric exclusion) inside a single-file channel that make it easy for two glycerol molecules cooperatively to move one substrate molecule across the AQGP channel via the high affinity site.…”

Section: Introductionmentioning

confidence: 99%

Aquaglyceroporin AQP7’s affinity for its substrate glycerol

Falato

Chen

2021

Preprint

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AQP7 is one of the four human aquaglyceroporins that facilitate glycerol transport across the cell membrane, a biophysical process that is essential in human physiology. Therefore, it is interesting to compute AQP7’s affinity for its substrate (glycerol) with reasonable certainty to compare with the experimental data suggesting high affinity in contrast with most computational studies predicting low affinity. In this study aimed at computing the AQP7-glycerol affinity with high confidence, we implemented a direct computation of the affinity from unbiased equilibrium molecular dynamics (MD) simulations of three all-atom systems constituted with 0.16M, 4.32M, and 10.23M atoms, respectively. These three sets of simulations manifested a fundamental physics law that the intrinsic fluctuations of pressure in a system are inversely proportional to the system size (the number of atoms in it). These simulations showed that the computed values of glycerol-AQP7 affinity are dependent upon the system size (the inverse affinity estimations were, respectively, 47.3 mM, 1.6 mM, and 0.92 mM for the three model systems). In this, we obtained a lower bound for the AQP7-glycerol affinity (an upper bound for the dissociation constant). Namely, the AQP7-glycerol affinity is stronger than 1087/M (the dissociation constant is less than 0.92 mM). Additionally, we conducted hyper steered MD (hSMD) simulations to map out the Gibbs free-energy profile. From the free-energy profile, we produced an independent computation of the AQP7-glycerol dissociation constant being approximately 0.18 mM.Table of contents entry

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Quantitative study of unsaturated transport of glycerol through aquaglyceroporin that has high affinity for glycerol

Abstract: In addition to the single-glycerol mechanism for saturable kinetics, a second transport pathway becomes more significant at higher substrate concentrations, resulting in unsaturable transport characteristics of an aquaglyceroporin.

Cited by 5 publications

References 99 publications

Characterization of SIPs-type aquaporins and their roles in response to environmental cues in rice (Oryza sativa L.)

Characterization of SIPs-type aquaporins and their roles in response to environmental cues in rice (Oryza sativa L.)

Aquaglyceroporin AQP7's affinity for its substrate glycerol. Have we reached convergence in the computed values of glycerol-aquaglyceroporin affinity?

Aquaglyceroporin AQP7’s affinity for its substrate glycerol

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