3.A.10 The H+, Na+-translocating Pyrophosphatase (M+-PPase) Family

Proteins of the H+-PPase family are found in the vacuolar (tonoplast) membranes of higher plants, algae, and protozoa, and in both bacteria and archaea. They are therefore ancient enzymes. The plant enzymes probably pump one H+ upon hydrolysis of pyrophosphate, thereby generating a proton motive force, positive and acidic in the tonoplast lumen. They establish a pmf of similar magnitude to that generated by the H+-translocating ATPases in the same vacuolar membrane. The bacterial and archaeal proteins may catalyze fully reversible reactions, thus being able to synthesize pyrophosphate when the pmf is sufficient. The enzyme from R. rubrum contributes to the pmf when light intensity is insufficient to generate a pmf sufficient in magnitude to support rapid ATP synthesis. Both C-termini of the dimeric subunits of V-PPase are on the same side of the membrane, and they are close to each other (Liu et al., 2009). Transmembrane domain 6 of vacuolar H+-pyrophosphatase appears to mediate both protein targeting and proton transport (Pan et al., 2010).

Eukaryotic members of the H+-PPase family are large proteins of about 770 amino acyl residues with fifteen or sixteen putative transmembrane α-helical spanners (TMSs). The N-termini are predicted to be in the vacuolar lumen while the C-termini are thought to be in the cytoplasm. These proteins exhibit a region that shows convincing sequence similarity to the regions surrounding the DCCD-sensitive glutamate in the C-terminal regions of the c-subunits of F-type ATPases (TC #3.A.2). The H+-pyrophosphatase of Streptomyces coelicolor has been shown to have a 17 TMS topology with the substrate binding domain exposed to the cytoplasm. The C-terminus is hydrophilic with a single C-terminal TMS. The basic structure is believed to have 16 TMSs with several large cytoplasmic loops containing functional motifs (Mimura et al., 2004). Several acidic residues in the Arabidopsis H+-PPase have been shown to be important for function. Some plants possess closely related H+-PPase isoforms. These enzymes have the enzyme commission number EC 3.6.1.1.

Full-length members of the H+-PPase family have been sequenced from numerous bacteria, archaea and eukaryotes. These H+ pumping enzymes, which are probably homodimeric, have been reported to fall into two phylogenetic subfamilies (Belogurov et al., 2002). One subfamily invariably contains a conserved cysteine (Cys222) and includes all known K+-independent H+-PPases while the other has another conserved cysteine (Cys573) but lacks Cys222 and includes all known K+-dependent H+-PPases (Belogurov et al., 2000). All H+-PPases require Mg2+, and those from plant vacuoles, acidocalcisomes of protozoa and fermentative bacteria require mM K+. Those from respiratory and photosynthetic bacteria as well as archaea are less dependent on K+. However, exceptions may exist (Belogurov et al., 2000). It is not sure whether K+ is transported.

The archaeon, Methanosarcina mazei Gö1, encodes within its genome two H+-translocating pyrophosphatases, Mvp1 and Mvp2. Mvp1 resembles bacterial PPases while Mvp2 resembles plant PPases (Bäumer et al., 2002). Mvp2 was shown to translocate 1 H+ per pyrophosphate hydrolyzed.

Some PPases from Anaerostipes caccae, Chlorobium limicola, Clostridium tetani, and Desulfuromonas acetoxidans have been identified as K+-dependent Natransporters (Luoto et al., 2011). Phylogenetic analysis led to the identification of a monophyletic clade comprising characterized and predicted Na+-transporting PPases (Na+-PPases) within the K+-dependent subfamily. H+-transporting PPases (H+-PPases) are more heterogeneous and form at least three independent clades in both subfamilies (Luoto et al., 2011).

Lin et al. (2012) reported the crystal structure of a Vigna radiata H+-PPase (VrH+-PPase) in complex with a non-hydrolysable substrate analogue, imidodiphosphate (IDP), at 2.35 Å resolution. Each VrH+-PPase subunit consists of an integral membrane domain formed by 16 transmembrane helices. IDP is bound in the cytosolic region of each subunit and trapped by numerous charged residues and five Mg2+ ions. A previously undescribed proton translocation pathway is formed by six core transmembrane helices. Proton pumping can be initialized by PP(i) hydrolysis, and H+ is then transported into the vacuolar lumen through a pathway consisting of Arg 242, Asp 294, Lys 742 and Glu 301. Lin et al. (2012) proposed a working model of the mechanism for the coupling between proton pumping and PP(i) hydrolysis by H+-PPases. 

Membrane-integral pyrophosphatases (M-PPases) are crucial for the survival of plants, bacteria, and protozoan parasites. They couple pyrophosphate hydrolysis or synthesis to Na+ or Hpumping. The 2.6Å structure of Thermotoga maritima H+-PPase in the resting state revealed a previously unknown solution for ion pumping (Kellosalo et al., 2012). The hydrolytic center, 20 angstroms above the membrane, is coupled to the gate formed by the conserved Asp(243), Glu(246), and Lys(707) by an unusual 'coupling funnel' of six α helices. Helix 12 slides down upon substrate binding to open the gate by a simple binding-change mechanism. Below the gate, four helices form the exit channel. Superimposing helices 3 to 6, 9 to 12, and 13 to 16 suggests that M-PPases arose through gene triplication. By comparing the active sites, fluoride inhibition data and the various models for ion transport, Kajander et al. (Kajander et al. 2013) concluded that membrane-integral PPases probably use binding of pyrophosphate to drive pumping. 

Membrane-bound pyrophosphatases (mPPases) are divided into K+,Na+-independent, Na+-regulated, and K+-dependent families. The first two families include H+-transporting mPPases (H+-PPases), whereas the last family comprises one Na+-transporting, two Na+-and H+-transporting subfamilies (Na+-PPases and Na+,H+-PPases, respectively), and three H+-transporting subfamilies (Artukka et al. 2018). Studies of the few available model mPPases suggested that K+ binds to a site located adjacent to the pyrophosphate-binding site but is substituted by the epsilon-amino group of a lysine residue in the K+-independent mPPases. Artukka et al. 2018 performed a systematic analysis of the K+/Lys cationic center across all mPPase subfamilies. An Ala-->Lys replacement in K+-dependent mPPases abolished the K+ dependence of hydrolysis and transport activities and decreased these activities to the level (4-7%) observed for wild-type enzymes in the absence of monovalent cations. In contrast, a Lys-->Ala replacement in K+,Na+-independent mPPases conferred partial K+ dependence on the enzyme by unmasking an otherwise conserved K+-binding site. Na+ could partially replace K+ as activator of K+-dependent mPPases and the Lys-->Ala variants of K+,Na+-independent mPPases. All mPPases were inhibited by excess substrate, suggesting strong negative cooperativity of active site functioning in these homodimeric enzymes. The K+/Lys center was identified as part of the mechanism underlying this effect. Possibly mPPase homodimers possess asymmetric active sites that may be an ancient prototype of the rotational binding-change mechanism of F-type ATPases (Artukka et al. 2018).

H+- and Na+-PPases are distributed in various organisms including plants, parasitic protozoa, archaea and bacteria, but are not present in animals or yeast (Segami et al. 2018).  Acidification performed with the vacuolar-type H+-ATPase and H+-PPase is essential to maintain acidic conditions, which are necessary for vacuolar hydrolytic enzymes and for supplying energy to secondary active transporters. The physiological importance of the scavenging role of PPi has come to light. An overview of the main features of H+-PPases present in the vacuolar membrane is provided by Segami et al. 2018 in terms of tissue distribution in plants, intracellular localizations, structure-function relationships, biochemical potential as proton pumps and functional stability.

The generalized transport reaction catalyzed by H+ (or Na+)-PPases is:

pyrophosphate (P2) + H2O + H+ (or Na+) (cytoplasm) → inorganic phosphate (2 Pi) + H+ (or Na+) (external milieu or vacuolar lumen)



This family belongs to the .

 

References:

Artukka, E., H.H. Luoto, A.A. Baykov, R. Lahti, and A.M. Malinen. (2018). Role of the potassium/lysine cationic center in catalysis and functional asymmetry in membrane-bound pyrophosphatases. Biochem. J. [Epub: Ahead of Print]

Bäumer, S., S. Lentes, G. Gottschalk, and U. Deppenmeier. (2002). Identification and analysis of proton-translocating pyrophosphatases in the methanogenic archaeon Methansarcina mazei. Archaea 1: 1-7.

Baltscheffsky, H. and B. Persson. (2014). On an Early Gene for Membrane-Integral Inorganic Pyrophosphatase in the Genome of an Apparently Pre-LUCA Extremophile, the Archaeon Candidatus Korarchaeum cryptofilum. J. Mol. Evol. 78: 140-147.

Baltscheffsky, M. and H. Baltscheffsky. (1993). Inorganic pyrophosphate and inorganic pyrophosphatases. In: L. Ernster ( ed.), Molecular Mechanisms in Bioenergetics. Amsterdam, The Netherlands: Elsevier Science Publishers B.V., pp. 331-348.

Baltscheffsky, M., A. Schultz, and H. Baltscheffsky. (1999). H+ -PPases: a tightly membrane-bound family. FEBS Lett. 457: 527-533.

Belogurov, G.A., M.V. Turkina, A. Penttinen, S. Huopalahti, A.A. Baykov, and R. Lahti. (2002). H+-pyrophosphatase of Rhodospirillum rubrum. High yield expression in Escherichia coli and identification of the Cys residues responsible for inactivation by mersalyl. J. Biol. Chem. 277: 22209-22214.

Charles, H., S. Balmand, A. Lamelas, L. Cottret, V. Pérez-Brocal, B. Burdin, A. Latorre, G. Febvay, S. Colella, F. Calevro, and Y. Rahbé. (2011). A genomic reappraisal of symbiotic function in the aphid/Buchnera symbiosis: reduced transporter sets and variable membrane organisations. PLoS One 6: e29096.

Chen, Y.W., C.H. Lee, Y.T. Huang, Y.J. Pan, S.M. Lin, Y.Y. Lo, C.H. Lee, L.K. Huang, Y.F. Huang, Y.D. Hsu, and R.L. Pan. (2014). Functional and fluorescence analyses of tryptophan residues in H+-pyrophosphatase of Clostridium tetani. J. Bioenerg. Biomembr. 46: 127-134.

Drozdowicz, Y.M., J.C. Kissinger, and P.A. Rea. (2000). AVP2, a sequence-divergent, K(+)-insensitive H(+)-translocating inorganic pyrophosphatase from Arabidopsis. Plant Physiol. 123: 353-62.

Drozdowicz, Y.M., M. Shaw, M. Nishi, B. Striepen, H.A. Liwinski, D.S. Roos, and P.A. Rea. (2003). Isolation and characterization of TgVP1, a type I vacuolar H+-translocating pyrophosphatase from Toxoplasma gondii. The dynamics of its subcellular localization and the cellular effects of a diphosphonate inhibitor. J. Biol. Chem. 278: 1075-1085.

Drozdowicz, Y.M., Y.-P. Lu, V. Patel, S. Fitz-Gibbon, J.H. Miller, and P.A. Rea. (1999). A thermostable vacuolar-type membrane pyrophosphatase from the archaeon Pyrobaculum aerophilum: implication for the origins of pyrophosphate-energized pumps. FEBS Lett. 460: 505-512.

Gaxiola, R.A., J. Li, S. Undurraga, L.M. Dang, G.J. Allen, S.L. Alper, and G.R. Fink. (2001). Drought- and salt-tolerant plants result from overexpression of the AVP1 H+-pump. Proc. Natl. Acad. Sci. USA 98: 11444-11449.

Hernández, A., R. Herrera-Palau, J.M. Madroñal, T. Albi, G. López-Lluch, J.R. Perez-Castiñeira, P. Navas, F. Valverde, and A. Serrano. (2016). Vacuolar H+-Pyrophosphatase AVP1 is Involved in Amine Fungicide Tolerance in Arabidopsis thaliana and Provides Tridemorph Resistance in Yeast. Front Plant Sci 7: 85.

Hirono, M., Y. Nakanishi, and M. Maeshima. (2007). Identification of amino acid residues participating in the energy coupling and proton transport of Streptomyces coelicolor A3(2) H+-pyrophosphatase. Biochim. Biophys. Acta. 1767: 1401-1411.

Hsu, S.H., Y.Y. Lo, T.H. Liu, Y.J. Pan, Y.T. Huang, Y.J. Sun, C.C. Hung, F.G. Tseng, C.W. Yang, and R.L. Pan. (2015). Substrate-induced changes in domain interaction of vacuolar H⁺-pyrophosphatase. J. Biol. Chem. 290: 1197-1209.

Huang YT., Liu TH., Lin SM., Chen YW., Pan YJ., Lee CH., Sun YJ., Tseng FG. and Pan RL. (2013). Squeezing at entrance of proton transport pathway in proton-translocating pyrophosphatase upon substrate binding. J Biol Chem. 288(27):19312-20.

Kajander T., Kellosalo J. and Goldman A. (2013). Inorganic pyrophosphatases: one substrate, three mechanisms. FEBS Lett. 587(13):1863-9.

Kellosalo, J., T. Kajander, K. Kogan, K. Pokharel, and A. Goldman. (2012). The structure and catalytic cycle of a sodium-pumping pyrophosphatase. Science 337: 473-476.

Kim, E.J., R.G. Zhen, and P.A. Rea. (1994). Heterologous expression of plant vacuolar pyrophosphatase in yeast demonstrates sufficiency of the substrate-binding subunit for proton transport. Proc. Natl. Acad. Sci. USA 91: 6128-6132.

Li, J., H. Yang, W.A. Peer, G. Richter, J. Blakeslee, A. Bandyopadhyay, B. Titapiwantakun, S. Undurraga, M. Khodakovskaya, E.L. Richards, B. Krizek, A.S. Murphy, S. Gilroy, and R. Gaxiola. (2005). Arabidopsis H+-PPase AVP1 regulates auxin-mediated organ development. Science 310: 121-125.

Lin, S.M., J.Y. Tsai, C.D. Hsiao, Y.T. Huang, C.L. Chiu, M.H. Liu, J.Y. Tung, T.H. Liu, R.L. Pan, and Y.J. Sun. (2012). Crystal structure of a membrane-embedded H+-translocating pyrophosphatase. Nature 484: 399-403.

Liu, T.H., S.H. Hsu, Y.T. Huang, S.M. Lin, T.W. Huang, T.H. Chuang, S.K. Fan, C.C. Fu, F.G. Tseng, and R.L. Pan. (2009). The proximity between C-termini of dimeric vacuolar H+-pyrophosphatase determined using atomic force microscopy and a gold nanoparticle technique. FEBS J. 276: 4381-4394.

Luoto, H.H., A.A. Baykov, R. Lahti, and A.M. Malinen. (2013). Membrane-integral pyrophosphatase subfamily capable of translocating both Na+ and H+. Proc. Natl. Acad. Sci. USA 110: 1255-1260.

Luoto, H.H., E. Nordbo, A.A. Baykov, R. Lahti, and A.M. Malinen. (2013). Membrane Na+-pyrophosphatases can transport protons at low sodium concentrations. J. Biol. Chem. 288: 35489-35499.

Luoto, H.H., E. Nordbo, A.M. Malinen, A.A. Baykov, and R. Lahti. (2015). Evolutionarily divergent, Na+-regulated H+-transporting membrane-bound pyrophosphatases. Biochem. J. 467: 281-291.

Luoto, H.H., G.A. Belogurov, A.A. Baykov, R. Lahti, and A.M. Malinen. (2011). Na+-translocating membrane pyrophosphatases are widespread in the microbial world and evolutionarily precede H+-translocating pyrophosphatases. J. Biol. Chem. 286: 21633-21642.

Malinen, A.M., G.A. Belogurov, A.A. Baykov, and R. Lahti. (2007). Na+-pyrophosphatase: a novel primary sodium pump. Biochemistry 46: 8872-8878.

Meng, X., Z. Xu, and R. Song. (2011). Molecular cloning and characterization of a vacuolar H+₋pyrophosphatase from Dunaliella viridis. Mol Biol Rep 38: 3375-3382.

Mimura, H., Y. Nakanishi, M. Hirono, and M. Maeshima. (2004). Membrane topology of the H+-pyrophosphatase of Streptomyces coelicolor determined by cysteine-scanning mutagenesis. J. Biol. Chem. 279: 35106-35112.

Pan YJ., Lee CH., Hsu SH., Huang YT., Lee CH., Liu TH., Chen YW., Lin SM. and Pan RL. (2011). The transmembrane domain 6 of vacuolar H(+)-pyrophosphatase mediates protein targeting and proton transport. Biochim Biophys Acta. 1807(1):59-67.

Rea, P.A. and R.J. Poole. (1993). Vacuolar H+-translocating pyrophosphatase. Ann. Rev. Plant Physiol. Plant Mol. Biol. 44: 157-180.

Ruiz, F.A., N. Marchesini, M. Seufferheld, Govindjee, and R. Docampo. (2001). The polyphosphate bodies of Chlamydomonas reinhardtii possess a proton-pumping pyrophosphatase and are similar to acidocalcisomes. J. Biol. Chem. 276: 46196-46203.

Schöcke, L. and B. Schink. (1998). Membrane-bound proton-translocating pyrophosphatase of Synthrophus gentianae,a syntrophically benzoate-degrading fermenting bacterium. Eur. J. Biochem. 256: 589-594.

Scholz-Starke, J., C. Primo, J. Yang, R. Kandel, R.A. Gaxiola, and K.D. Hirschi. (2019). The flip side of the type I proton-pumping pyrophosphatase (AVP1): Using a transmembrane H gradient to synthesize pyrophosphate. J. Biol. Chem. 294: 1290-1299.

Segami, S., M. Asaoka, S. Kinoshita, M. Fukuda, Y. Nakanishi, and M. Maeshima. (2018). Biochemical, Structural and Physiological Characteristics of Vacuolar H+-Pyrophosphatase. Plant Cell Physiol. 59: 1300-1308.

Wang, C.S., Q.T. Jiang, J. Ma, X.Y. Wang, J.R. Wang, G.Y. Chen, P.F. Qi, Y.Y. Peng, X.J. Lan, Y.L. Zheng, and Y.M. Wei. (2016). Characterization and expression analyses of the H⁺-pyrophosphatase gene in rye. J Genet 95: 565-572.

Yue, G., Z. Sui, Q. Gao, and J. Zhang. (2008). Molecular cloning and characterization of a novel H+-translocating pyrophosphatase gene in Zea mays. DNA Seq 19: 79-86.

Zhang, J., J. Li, X. Wang, and J. Chen. (2011). OVP1, a vacuolar H+-translocating inorganic pyrophosphatase (V-PPase), overexpression improved rice cold tolerance. Plant Physiol. Biochem 49: 33-38.

Zhen, R.-G., E.J. Kim, and P.A. Rea. (1997b). The molecular and biochemical basis of pyrophosphate-energized proton translocation at the vacuolar membrane. Adv. Bot. Res. 25: 297-337.

Zhen, R.G., E.J. Kim, and P.A. Rea. (1997). Acidic residues necessary for pyrophosphate-energized pumping and inhibition of the vacuolar H+-pyrophosphatase by N,N'-dicyclohexylcarbodiimide. J. Biol. Chem. 272: 22340-22348.

Examples:

TC#NameOrganismal TypeExample
3.A.10.1.1

H+-translocating vacuolar (tonoplast) pyrophosphatase of 770 aas, AVP1. 87% identical to the ortholog in rye (Secale cereale), found in the plasma membrane with 762 aas and 14 TMSs, ScHP1 (Wang et al. 2016). t contributes to the trans-tonoplast (from cytosol to vacuole lumen) H+-electrochemical potential difference and establishes a proton gradient of similar and often greater magnitude than the H+-ATPase in the same membrane (Kim et al. 1994). It also facilitates auxin transport by modulating the apoplastic pH, and it regulates auxin-mediated developmental processes (Li et al. 2005). It confers tolerance to NaCl and to drought by increasing ion retention (Gaxiola et al. 2001). H+-pyrophosphatases are major determinants of plant tolerance to amine fungicides (Hernández et al. 2016). As expected, a pmf can be used via AVP1 to make pyrophosphate (Scholz-Starke et al. 2019).

Plant vacuoles

V-PPase of Arabidopsis thaliana

 
3.A.10.1.10

The K -stimulated H ,Na -PPase. Transports both Na  and H  noncompetitively in a single catalytic cycle (Luoto et al. 2013).

Bacteria

H+,Na+-PPase of Bacteroides vulgatus (A6L2M4) 

 
3.A.10.1.11

The K+-stimulated H+, Na+-PPase.  Transports both Na+ and H+ noncompetitively in a single catalytic cycle (Luoto et al., 2013a, b).

Bacteria

H+, Na+-PPase of Prevotella oralis (E7RS29)

 
3.A.10.1.12

The K+-stimulated H+, Na+-PPase. Transports both Na+ and H+ noncompetitively in a single catalytic cycle (Luoto et al., 2013a, b).

Bacteria

H+, Na+-PPase of Verucomicrobiae bacterium (B5JQT8)

 
3.A.10.1.13

The K+-stimulated H , Na +-PPase.  Transports both Na + and H + noncompetitively in a single catalytic cycle (Luoto et al., 2013a, b).

Bacteria

The K -stimulated H , Na -PPase of Clostridium leptum

 
3.A.10.1.14

K+-stimulated Na+-PPase 

Archaea

K+-stimulated PPase of Methanosarcina mazei (Q8PYZ8)

 
3.A.10.1.15

K+-insensitive pyrophosphatase-energized proton pump of 665 aas (Baltscheffsky and Persson 2014).

Korarchaeota

PPase of Korarchaeum cryptofilum

 
3.A.10.1.16

Vacuolar H+-pyrophosphatase of 771 aas, Ovp1.  Expression increases cold tolerance in rice (Zhang et al. 2011).  Rice also have a similar paralogue, Ovp2, of 767 aas (P93410).  It is 88% identical to Ovp1.  The corn (Zea mays) orthologue of 766 aas and 16 TMSs (97% identical to the rice protein), Vpp1, is up-regulated in shoots and roots of maize seedlings under dehydration, cold and high salt stresses, suggesting a role in abiotic stress tolerance (Yue et al. 2008).

Plants

Ovp1 of Oriza sativa

 
3.A.10.1.17

H+-transporting pyrophosphatase of 816 aas (Drozdowicz et al. 2003). It is inhibited by 5-10 μM aminomethylenediphosphonate (AMDP) which also inhibits trypomastigotes and parasite growth (Drozdowicz et al. 2003).

H+-transporting pyrophosphatase of Toxoplasma gondii

 
3.A.10.1.2

H+-translocating acidocalcisome pyrophosphatase

Algae

V-PPase of Chlamydomonas reinhardtii

 
3.A.10.1.3Na+-translocating PPase (Malinen et al., 2007)BacteriaNa-PPase of Moorella thermoacetica (Q2RIS7)
 
3.A.10.1.4

Na+-translocating PPase (Malinen et al., 2007).  The 3-d resting state structure has been solved to 2.6 Å (Kellosalo et al. 2012).  The structure shows that the hydrolytic center is 20 Å above the membrane, coupled to the gate formed by the conserved Asp(243), Glu(246) and Lys(707) by an unusual "coupling funnel" of six α-helices. Helix 12 may slide down upon substrate binding to open the gate by a simple binding-change mechanism. Below the gate, four helices form the exit channel. Superimposing helices 3 to 6, 9 to 12, and 13 to 16 suggests that this PPases arose by gene triplication (Kellosalo et al. 2012).

Bacteria

Na+-PPase of Thermatoga maritima (Q9S5X0)

 
3.A.10.1.5

Na+-transporting, K+-dependent pyrophosphatase (Luoto et al., 2011).

Bacteria

Na+-pyrophosphatase of Anaerostipes caccae (B0M926)

 
3.A.10.1.6

Na+-transporting, K+-dependent pyrophosphatase (Luoto et al., 2011).

Bacteria

Na+-pyrophosphatase of Chloronbium limicola (B3ECG6)

 
3.A.10.1.7

K+-activated, H+-transporting pyrophosphatase, H+-PPase (Huang et al. 2013).  Trp-602 is a crucial residue that may stabilize the structure of the catalytic region (Chen et al. 2014).

Firmicutes

H+-PPase of Chlostridium tetani (Q898Q9)

 
3.A.10.1.8

Vacuolar H+-PPase. 3-d structure known at 2.3 Å resolution (Charles et al., 2011; Lin et al. 2012).  Each  subunit consists of an integral membrane domain formed by 16 transmembrane helices.  imidodiphosphate is bound in the cytosolic surface of each subunit and trapped by numerous charged residues and five Mg2+ ions. A proton translocation pathway is formed by six core transmembrane helices. Proton pumping is initialized by PPi hydrolysis, and H+ is then transported into the vacuolar lumen through a pathway consisting of Arg242, Asp294, Lys742 and Glu301 (Lin et al. 2012).  Substrate binding induces changes in domain interactions (Hsu et al. 2015).

Plants (mung bean)

H+-PPase of Vigna radiata (P21616)

 
3.A.10.1.9

Vacuolar proton-translocating pyrophosphatase (Meng et al. 2011).

Halotolerant algae

Proton-PPase of Dunaliella viridis

 
Examples:

TC#NameOrganismal TypeExample
3.A.10.2.1

H+-translocating pyrophosphatase (PPiase)/synthase.  It has two distinct roles depending on its location, acting as a PPi hydrolyzing intracellular proton pump in acidocalcisomes but as a PPi synthetase in the chromatophore membranes (Seufferheld et al. 2004).

Bacteria

H+-PPase of Rhodospirillum rubrum (O68460)

 
3.A.10.2.2

H+-translocating pyrophosphatase. This protein has a basic 16 TMS topology with several large cytoplasmic loops containing functional motifs as well as one or two C-terminal TMS(s) (Mimura et al., 2004).  Residues involved in energy coupling and proton transport have been identified (Hirono et al. 2007).

Bacteria

H+-PPase of Streptomyces coelicolor (Q6BCL0)

 
3.A.10.2.3Vacuolar Ca2+-hypersenstive, K+-insensitive, H+ -translocating, inorganic pyrophosphatase, AVP2 (Drozdowicz et al., 2000)PlantsAVP2 of Arabidopsis thaliana (Q56ZN6)
 
3.A.10.2.4Na+ -translocating PPase (Malinen et al., 2007)ArchaeaNa+ -PPase of Methanosarcina mazei (Q8PYZ7)
 
Examples:

TC#NameOrganismal TypeExample
3.A.10.3.1H+-translocating pyrophosphatase Archaea H+-PPase of Pyrobaculum aerophilum
 
3.A.10.3.2
Membrane-bound sodium- and potassium-regulated, proton-translocating pyrophosphatase of 806 aas. One report claims it transports only H+, not Na+ and that Na+ inhibits by competing with Mg2+ (Luoto et al. 2015), although a previous report claimed that it transports Na+ under normal physiological conditions, but protons if the Na+ concentration is low (Luoto et al. 2013).

Chlorobi

Na+/H+-PPase of Chlorobium limicola

 
3.A.10.3.3

Electrogenic H+-translocating Mg2+-pyrophosphatase, HhpA of 867 aas.  Inhibited by Na+ and regulated by K+ as well (Luoto et al. 2015).

Actinobacteria

P2ase of Cellulomonas fimi

 
3.A.10.3.4

H+ or Na+-translocating pyrophosphatase of 797 aas, HppA (Luoto et al. 2015).

Bacteroidetes

Pyrophosphatase of Azobacteroides pseudotrichonymphae genomovar. CFP2

 
3.A.10.3.5

H+-translocating pyrophosphatase of 836 aas, HppA (Luoto et al. 2015)

Proteobacteria

P2ase of Accumulibacter phosphatis