Thermodynamic cooperativity of cosubstrate binding and cation selectivity of <i>Salmonella typhimurium</i> MelB

Hariharan, Parameswaran; Guan, Lan

doi:10.1085/jgp.201711788

Cited by 34 publications

(77 citation statements)

References 47 publications

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“…We also note, however, that the chemical makeup and structure of the N-lobe Na + -binding site indicates that it is weakly Na + -specific against H + ; indeed, Na + coupling in MATEs likely results from the fact that Na + is in large excess over H + in most settings. This phenomenon is not uncommon; inherently H +selective sites that mediate Na + -driven activity in physiologically realistic conditions have been reported for other membrane enzymes and transporters, such as rotary ATP synthases (27,41) and amino acid and sugar symporters (42,43). This promiscuity between Na + and H + , modulated by the specific protein environment, would explain the observation of H + -driven function or other pH-dependent effects in MATEs featuring the Na + -binding motif described here.…”

Section: Discussionsupporting

confidence: 65%

Broadly conserved Na ⁺ -binding site in the N-lobe of prokaryotic multidrug MATE transporters

Ficici

Zhou

Faraldo‐Gómez

2018

Proc. Natl. Acad. Sci. U.S.A.

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Multidrug and toxic-compound extrusion (MATE) proteins comprise an important but largely uncharacterized family of secondary-active transporters. In both eukaryotes and prokaryotes, these transporters protect the cell by catalyzing the efflux of a broad range of cytotoxic compounds, including human-made antibiotics and anticancer drugs. MATEs are thus potential pharmacological targets against drug-resistant pathogenic bacteria and tumor cells. The activity of MATEs is powered by transmembrane electrochemical ion gradients, but their molecular mechanism and ion specificity are not understood, in part because high-quality structural information is limited. Here, we use computational methods to study PfMATE, from , whose structure is the best resolved to date. Analysis of available crystallographic data and additional molecular dynamics simulations unequivocally reveal an occupied Na-binding site in the N-lobe of this transporter, which had not been previously recognized. We find this site to be selective against K and broadly conserved among prokaryotic MATEs, including homologs known to be Na-dependent such as NorM-VC, VmrA, and ClbM, for which the location of the Na site had been debated. We note, however, that the chemical makeup of the proposed Na site indicates it is weakly specific against H, explaining why MATEs featuring this Na-binding motif may be solely driven by H in laboratory conditions. We further posit that the concurrent coupling to H and Na gradients observed for some Na-driven MATEs owes to a second H-binding site, within the C-lobe. In summary, our study provides insights into the structural basis for the complex ion dependency of MATE transporters.

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Section: Discussionsupporting

confidence: 65%

Broadly conserved Na ⁺ -binding site in the N-lobe of prokaryotic multidrug MATE transporters

Ficici

Zhou

Faraldo‐Gómez

2018

Proc. Natl. Acad. Sci. U.S.A.

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“…Channel's SF. The apparent K + -binding affinity for the KcsA's SF under equilibrium conditions was measured by isothermal titration calorimetry (ITC), as has been done before for measuring the apparent cation-binding affinity to membrane transporters (31,32). This measurement is considered an apparent ion-binding affinity because it was performed in the presence of 100-mM Na + ions, which could compete against K + ions for the SF's ion-binding sites.…”

Section: Ion-binding Properties Of the 24-ion-bound Configuration Ofmentioning

confidence: 99%

Structure, function, and ion-binding properties of a K ⁺ channel stabilized in the 2,4-ion–bound configuration

Tilegenova

Cortés

Jahovic

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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Here, we present the atomic resolution crystallographic structure, the function, and the ion-binding properties of the KcsA mutants, G77A and G77C, that stabilize the 2,4-ion–bound configuration (i.e., water, K+, water, K+-ion–bound configuration) of the K+ channel’s selectivity filter. A full functional and thermodynamic characterization of the G77A mutant revealed wild-type–like ion selectivity and apparent K+-binding affinity, in addition to showing a lack of C-type inactivation gating and a marked reduction in its single-channel conductance. These structures validate, from a structural point of view, the notion that 2 isoenergetic ion-bound configurations coexist within a K+ channel’s selectivity filter, which fully agrees with the water–K+-ion–coupled transport detected by streaming potential measurements.

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“…S1, blue); Residues Tyr120, Asp124, and Lys377 (Fig. S1, purple) may be shared by both binding sites [24,25].…”

Section: Discussionmentioning

confidence: 99%

“…2A, left). Although human TMEM180 has only 19% sequence identity with stMelB, comparison of the crystal structure of stMelB with the homology model of human TMEM180 revealed that five putative cation-binding residues (Asn63, Asn66, Asp67, Thr139, and Asp142) in the homology model were located in positions similar to those of five cation-binding residues of stMelB (Asp55, Asn58, Asp59, Thr121, and Asp124) [24,25] ( Fig. 2A,B).…”

Section: Homology Modeling Of Human Tmem180mentioning

confidence: 99%

Topological analysis of TMEM180, a newly identified membrane protein that is highly expressed in colorectal cancer cells

Anzai

Matsumura

2019

Preprint

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New target molecules for diagnosis of and drug development for colorectal cancer (CRC) are always in great demand. Previously, we identified a new colorectal cancer-specific protein, TMEM180, and successfully developed an anti-TMEM180 monoclonal antibody (mAb) for the diagnosis and treatment of CRC. Although TMEM180 is categorized as a member of the cation symporter family and multi-pass membrane protein, little is known about its function. In this study, we examined topology of this membrane protein and analyzed its function. Using a homology model of human TMEM180, we experimentally determined that the protein has 12 transmembrane domains, and that its N-terminal and C-termini are exposed extracellularly. Moreover, we found that the putative cation-binding site of TMEM180 is conserved among orthologs, and that its position is similar to that of melibiose transporter MelB. These results suggest that TMEM180 acts as a cation symporter. Our topological analysis based on the homology model provides insight into functional and structural roles of TMEM180 that may help to elucidate the pathology of CRC. Highlights・A homology model of human TMEM180 was generated by secondary structure prediction.・Putative cation-binding residues are conserved in TMEM180 orthologs.・Both the N-terminus and C-terminus of TMEM180 are extracellularly exposed.・TMEM180 is a 12-transmembrane protein.・TMEM180 could act as a cation symporter. KeywordsTMEM180, MFSD13A, cation symporter, homology model, colorectal cancer Abbreviations TMEM180, transmembrane protein 180; MFSD13A, major facilitator superfamily domaincontaining 13A; mAb, monoclonal antibody; pAb, polyclonal antibody; CRC, colorectal cancer; siRNA, small interfering RNA; shRNA, small hairpin RNA;

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Thermodynamic cooperativity of cosubstrate binding and cation selectivity of Salmonella typhimurium MelB

Abstract: The melibiose symporter MelB couples melibiose transport to that of cations such as Na+. Hariharan and Guan show that the binding of Na+ and melibiose is thermodynamically cooperative and that Na+ coupling is based on ion concentrations and competitive binding, but not ion selectivity.

Cited by 34 publications

References 47 publications

Broadly conserved Na ⁺ -binding site in the N-lobe of prokaryotic multidrug MATE transporters

Broadly conserved Na ⁺ -binding site in the N-lobe of prokaryotic multidrug MATE transporters

Structure, function, and ion-binding properties of a K ⁺ channel stabilized in the 2,4-ion–bound configuration

Topological analysis of TMEM180, a newly identified membrane protein that is highly expressed in colorectal cancer cells

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Thermodynamic cooperativity of cosubstrate binding and cation selectivity of Salmonella typhimurium MelB

Abstract: The melibiose symporter MelB couples melibiose transport to that of cations such as Na+. Hariharan and Guan show that the binding of Na+ and melibiose is thermodynamically cooperative and that Na+ coupling is based on ion concentrations and competitive binding, but not ion selectivity.

Cited by 34 publications

References 47 publications

Broadly conserved Na + -binding site in the N-lobe of prokaryotic multidrug MATE transporters

Broadly conserved Na + -binding site in the N-lobe of prokaryotic multidrug MATE transporters

Structure, function, and ion-binding properties of a K + channel stabilized in the 2,4-ion–bound configuration

Topological analysis of TMEM180, a newly identified membrane protein that is highly expressed in colorectal cancer cells

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Broadly conserved Na ⁺ -binding site in the N-lobe of prokaryotic multidrug MATE transporters

Broadly conserved Na ⁺ -binding site in the N-lobe of prokaryotic multidrug MATE transporters

Structure, function, and ion-binding properties of a K ⁺ channel stabilized in the 2,4-ion–bound configuration