Energy Coupling in Cation-Pumping Pyrophosphatase—Back to Mitchell

Baykov, Alexander A.

doi:10.3389/fpls.2020.00107

Cited by 11 publications

(23 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Vidilaseris et al assumed that these energies are used, respectively, for proton transport and product release, because they believed that transport precedes hydrolysis. Based on the reinterpretation [ 18 ] of the electrometric data reported by Goldman’s group [ 33 , 44 ], our model presumes that the transport event follows PP i hydrolysis and accordingly ascribes interchanged roles for the conformational and chemical energy. Second, our model does not require PP i binding to both subunits because such binding decreases the catalytic efficiency of mPPase, and can hardly be significant at the PP i concentrations expected in the cell.…”

Section: Discussionmentioning

confidence: 99%

“…That the transported H + ion is the one generated from the nucleophilic water ("direct coupling") is supported by the finding that H + transport occurs synchronously with PP i hydrolysis [18]. Hypothetically, the same water-generated proton can trigger Na + transport via a "billiards-type" mechanism in mPPase [18]. The crystal structure of the Vigna radiata membrane pyrophosphatase (mPPase) dimer [17].…”

Section: Introductionmentioning

confidence: 97%

“…Other mPPases are predicted to have very similar structures. That the transported H + ion is the one generated from the nucleophilic water (“direct coupling”) is supported by the finding that H + transport occurs synchronously with PP i hydrolysis [ 18 ]. Hypothetically, the same water-generated proton can trigger Na + transport via a “billiards-type” mechanism in mPPase [ 18 ].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Catalytic Asymmetry in Homodimeric H+-Pumping Membrane Pyrophosphatase Demonstrated by Non-Hydrolyzable Pyrophosphate Analogs

Anashkin

Malinen

Bogachev

et al. 2021

IJMS

Self Cite

View full text Add to dashboard Cite

Membrane-bound inorganic pyrophosphatase (mPPase) resembles the F-ATPase in catalyzing polyphosphate-energized H+ and Na+ transport across lipid membranes, but differs structurally and mechanistically. Homodimeric mPPase likely uses a “direct coupling” mechanism, in which the proton generated from the water nucleophile at the entrance to the ion conductance channel is transported across the membrane or triggers Na+ transport. The structural aspects of this mechanism, including subunit cooperation, are still poorly understood. Using a refined enzyme assay, we examined the inhibition of K+-dependent H+-transporting mPPase from Desulfitobacterium hafniensee by three non-hydrolyzable PPi analogs (imidodiphosphate and C-substituted bisphosphonates). The kinetic data demonstrated negative cooperativity in inhibitor binding to two active sites, and reduced active site performance when the inhibitor or substrate occupied the other active site. The nonequivalence of active sites in PPi hydrolysis in terms of the Michaelis constant vanished at a low (0.1 mM) concentration of Mg2+ (essential cofactor). The replacement of K+, the second metal cofactor, by Na+ increased the substrate and inhibitor binding cooperativity. The detergent-solubilized form of mPPase exhibited similar active site nonequivalence in PPi hydrolysis. Our findings support the notion that the mPPase mechanism combines Mitchell’s direct coupling with conformational coupling to catalyze cation transport across the membrane.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Catalytic Asymmetry in Homodimeric H+-Pumping Membrane Pyrophosphatase Demonstrated by Non-Hydrolyzable Pyrophosphate Analogs

Anashkin

Malinen

Bogachev

et al. 2021

IJMS

Self Cite

View full text Add to dashboard Cite

show abstract

“…6. Do Fe 3+ polarons in general act to pump anions nano-peristaltically into and/or through the green rust interlayers, as well as pump nutrients through, and toxins and uncooperative molecular waste out of, the system [ 6 , 72 , 315 , 316 , 317 , 318 , 324 , 338 ]?…”

Section: What’s Next For the Avt?mentioning

confidence: 99%

“…If so, can immediate hydrolyses leverage trapping of condensation reactions at neighboring (and oscillating) binding sites (cf. certain pyrophosphatases), i.e., can ‘macromolecular’ green rust effect alternating independent coupling as in the binding change mechanisms that are known to operate in enzymes such as the proton pyrophosphatases [ 72 , 228 , 315 , 316 , 317 , 318 ]?…”

Section: What’s Next For the Avt?mentioning

confidence: 99%

The “Water Problem”(sic), the Illusory Pond and Life’s Submarine Emergence—A Review

Russell

2021

Life

View full text Add to dashboard Cite

The assumption that there was a “water problem” at the emergence of life—that the Hadean Ocean was simply too wet and salty for life to have emerged in it—is here subjected to geological and experimental “reality checks”. The “warm little pond” that would take the place of the submarine alkaline vent theory (AVT), as recently extolled in the journal Nature, flies in the face of decades of geological, microbiological and evolutionary research and reasoning. To the present author, the evidence refuting the warm little pond scheme is overwhelming given the facts that (i) the early Earth was a water world, (ii) its all-enveloping ocean was never less than 4 km deep, (iii) there were no figurative “Icelands” or “Hawaiis”, nor even an “Ontong Java” then because (iv) the solidifying magma ocean beneath was still too mushy to support such salient loadings on the oceanic crust. In place of the supposed warm little pond, we offer a well-protected mineral mound precipitated at a submarine alkaline vent as life’s womb: in place of lipid membranes, we suggest peptides; we replace poisonous cyanide with ammonium and hydrazine; instead of deleterious radiation we have the appropriate life-giving redox and pH disequilibria; and in place of messy chemistry we offer the potential for life’s emergence from the simplest of geochemically available molecules and ions focused at a submarine alkaline vent in the Hadean—specifically within the nano-confined flexible and redox active interlayer walls of the mixed-valent double layer oxyhydroxide mineral, fougerite/green rust comprising much of that mound.

show abstract

Pre‐steady‐state kinetics and solvent isotope effects support the “billiard‐type” transport mechanism in Na⁺‐translocating pyrophosphatase

et al. 2022

Self Cite

View full text Add to dashboard Cite

Membrane‐bound pyrophosphatase (mPPase) found in microbes and plants is a membrane H+ pump that transports the H+ ion generated in coupled pyrophosphate hydrolysis out of the cytoplasm. Certain bacterial and archaeal mPPases can in parallel transport Na+ via a hypothetical “billiard‐type” mechanism, also involving the hydrolysis‐generated proton. Here, we present the functional evidence supporting this coupling mechanism. Rapid‐quench and pulse‐chase measurements with [32P]pyrophosphate indicated that the chemical step (pyrophosphate hydrolysis) is rate‐limiting in mPPase catalysis and is preceded by a fast isomerization of the enzyme‐substrate complex. Na+, whose binding is a prerequisite for the hydrolysis step, is not required for substrate binding. Replacement of H2O with D2O decreased the rates of pyrophosphate hydrolysis by both Na+‐ and H+‐transporting bacterial mPPases, the effect being more significant than with a non‐transporting soluble pyrophosphatase. We also show that the Na+‐pumping mPPase of Thermotoga maritima resembles other dimeric mPPases in demonstrating negative kinetic cooperativity and the requirement for general acid catalysis. The findings point to a crucial role for the hydrolysis‐generated proton both in H+‐pumping and Na+‐pumping by mPPases.

show abstract

Energy Coupling in Cation-Pumping Pyrophosphatase—Back to Mitchell

Cited by 11 publications

References 25 publications

Catalytic Asymmetry in Homodimeric H+-Pumping Membrane Pyrophosphatase Demonstrated by Non-Hydrolyzable Pyrophosphate Analogs

Catalytic Asymmetry in Homodimeric H+-Pumping Membrane Pyrophosphatase Demonstrated by Non-Hydrolyzable Pyrophosphate Analogs

The “Water Problem”(sic), the Illusory Pond and Life’s Submarine Emergence—A Review

Pre‐steady‐state kinetics and solvent isotope effects support the “billiard‐type” transport mechanism in Na⁺‐translocating pyrophosphatase

Contact Info

Product

Resources

About

Energy Coupling in Cation-Pumping Pyrophosphatase—Back to Mitchell

Cited by 11 publications

References 25 publications

Catalytic Asymmetry in Homodimeric H+-Pumping Membrane Pyrophosphatase Demonstrated by Non-Hydrolyzable Pyrophosphate Analogs

Catalytic Asymmetry in Homodimeric H+-Pumping Membrane Pyrophosphatase Demonstrated by Non-Hydrolyzable Pyrophosphate Analogs

The “Water Problem”(sic), the Illusory Pond and Life’s Submarine Emergence—A Review

Pre‐steady‐state kinetics and solvent isotope effects support the “billiard‐type” transport mechanism in Na+‐translocating pyrophosphatase

Contact Info

Product

Resources

About

Pre‐steady‐state kinetics and solvent isotope effects support the “billiard‐type” transport mechanism in Na⁺‐translocating pyrophosphatase