ATPase V-type

Hicks, B.W. and Parsons, S.M., 1992, Characterization of the P-type and V-type ATPases of cholinergic synaptic vesicles and coupling of nucleotide hydrolysis to acetylchohne transport. J. Neurochem., 58 1211-1220. 

P-type ATPases 398 SERCA pump 400 F-type ATPases 401 ATP synthase 401 V-type ATPases 401 ABC transporters 402 multidrug transporter 402... 

Enzymes that are structurally related to the eukaryotic V-ATPase are also found in certain eubacteria (Speelmans etal., 1994 Takase etal., 1994 Yokoyama etal., 1990). Based on nucleotide sequence analysis, it is believed that these bacterial V-like ATPases have been introduced into the eubacteria via horizontal gene transfer from Archaea (Hilario and Gogarten, 1993, 1998). The subunit composition of the bacterial V-like ATPase is indeed more similar to the archaeal A-ATPase than to the eukaryotic V-ATPase, and we will therefore treat the bacterial V-ATPase—like enzyme together with the archaeal A-ATPase (see below). In the following, we will use the name V-ATPase only for the eukaryotic enzyme, and we will call the bacterial enzyme the A/V-type ATPase as suggested by Hilario and Gogarten (1998). 

Based on sequence comparison, the eubacterial V-type ATPase is a product of horizontal gene transfer from the Archaea. Much of the information about the subunit arrangement in the eubacterial A/V-type—like ATPase comes from studies with the enzymes from C. fervidus and T. thermophilus (Boekema et al, 1997, 1999 Ubbink-Kok et al, 2000 Yokoyama et al, 2003a). A recent 3D reconstruction of the A/V- ATPase from T. thermophilus (Bernal and Stock, 2004) revealed the structural similarity to both the eukaryotic V-ATPase (Domgall et al., 2002 Wilkens et al., 2004, 2005) and the archaeal A-ATPase (Coskun et al., 2004a,b). The x-ray crystal structure for the C-subunit of the bacterial A/V-like ATPase has been reported recently (Iwata et al, 2004). The C-subunit of the bacterial V-like ATPase shows limited but significant sequence homology to the cZ-subunit of the eukaryotic V-ATPase. 

Boekema, E.J., Ubbink-Kok, T., Lolkema.J. S., Brisson, A., and Konings, W. N. (1997). Visualization of a peripheral stalk in V-type ATPase Evidence for the stator structure essential to rotational catalysis. Proc. Natl Acad. Sci. USA 94, 14291-14293. 

Sagermann, M., Stevens, T. H., and Matthews, B. W. (2001). Crystal structure of the regulatory subunit H of the V-type ATPase of Saccharomyces cerevisiae. Proc. Natl. Acad. Sci. USA 98, 7134-7139. 

Yokoyama, K., Oshima, T., and Yoshida, M. (1990). Thermus thermophilus membrane-associated ATPase Indication of a eubacterial V-type ATPase. J. Biol. Chem. 265, 21946-21950. 

Fig. 2. Kinetics of exocytosis, endocytosis, and reacidification of glutamatergic vesicles in astrocytes. (A) In the presence of Baf Al, a V-type ATPase inhibitor, VGLUT1 -pHluorin and vesicle lumens become trapped in the alkaline state after fusion. The signal represents a pure measure of exocytosis because reacidification is blocked (Ryan, 2001). (B) Astrocytes transfected with VGLUT 1-pHluorin have been stimulated with DHPG (100 fiM) and imaged with TIRFi...

The V-type (or vacuolar-type) H+-ATPase was first found in fungal vacuoles and plant tonoplasts,13 l4) and is now known to be widely distributed in mammalian endomembrane systems.15) Like F-type ATPase, the subunit structure of the V-type ATPase is complicated. The membrane extrinsic sector is composed of 73 kDa, 58 kDa, 38 kDa, and 34 kDa subunits, while the membrane intrinsic sector is composed of 40 kDa 20 kDa and 16 kDa subunits. 

Three types of ATP-driven cation pumps can be distinguished on the basis of their structure and their sensitivity to inhibitors. They are the E E2-ATPases, the FiFo-proton-translocating ATP synthase, and the vacuolar ATPases which are designated as P-, F-, and V-type ATPases, respectively [37]. Several of the distinguishing characteristics of these enzymes are summarized in Table 1. The F- and V-ATPases can be differentiated by the sensitivity of the former to azide and the latter to nitrate and A-ethylmaleimide (NEM)[38]. In addition, the V-ATPases are exquisitely sensitive to the antibiotic bafilomycin A [39,40]. 

The membrane-bound archaeal ATPases have attracted considerable interest since patterns of inhibitor sensitivity, subunit structure, and amino-acid sequence homologies suggest a close relationship to the V-type ATPases [3,41]. In addition, the membrane-bound ATPases from S. acidocaldarius, H. salinarium (halobium), Methanosarcina barken, and the V-type ATPase from Saccharomyces cerevisiae are immunologically related [42]. 

Methanococcus voltae contains a membrane-bound vanadate-sensitive ATPase [48] that is inhibited by diethylstilbestrol, an inhibitor of eukaryotic P-type ATPases. The purified enzyme is composed of a single subunit (Mr 74 000), forms a covalent acyl-phosphate enzyme intermediate, and is not inhibited by nitrate or bafilomycin [49]. No such ATPase activity has been reported in other archaea. The presence of a second ATPase in M. voltae has been inferred since membranes react with antiserum prepared against the 3 subunit from the V-type ATPase of S. acidocaldarius [50]. Two peptides are detected whose Mr values (51 000 and 65 000) correspond to the masses for the two laigest subunits of the S. acidocaldarius ATPase [51]. There is evidence that ATP synthesis in the M. voltae enzyme is due to the operation of a sodium-translocating ATPase [50]. The relationship of the putative V-like ATPase to the sodium-translocating ATPase has not been established. 

M thermoautotrophicum cells synthesize ATP in the presence of an artificially imposed pH gradient [18], Proton uptake is not detected following acidification. The addition of valinomycin results in the synthesis of ATP and is accompanied by the extrusion of K but not protons. ATP synthesis is unaffected by DCCD and is stimulated by uncouplers such as 2,4-dinitrophenol and m-chlorophenyl hydrazone. Membrane vesicles from M thermoautotrophicum synthesize ATP when conditions are anaerobic in response to the membrane potential since the addition of suppresses synthesis. ATP synthesis is inhibited by 100 pM CCCP and partially inhibited by DCCD (53% at 100 pM). ATP synthesis also takes place in response to a ApH produced by the oxidation of hydrogen. In this case, ATP synthesis is inhibited by lOpM DCCD and CCCP. Unlike cells, vesicles do not synthesize ATP in response to an artificially imposed ApH or in the presence of valinomycin [54]. M. thermoautotrophicum membranes have an ATPase activity that hydrolyzes ATP, GTP, and UTP at approximately the same rate. The enzyme loses activity at -90°C which is due to aggregation, and activity is restored following sonication. ATPase activity is partially inhibited by DCCD (40% at lOOpM) when membranes are incubated at pH 8 for 10 min [18]. A similar ATPase is found in a different strain of M. thermoautotrophicum [29]. The enzyme is most active at an alkaline pH and it is not significantly inhibited by ADP, 5mM NEM, or 150 pM DCCD. The absence of NEM inhibition suggests that the enzyme may not be a V-type ATPase. 

The nucleotide sequence derived from the gene for the DCCD-reactive proteolipid from S. acidocaldarius (strain 7) indicates that the peptide has an Mr of about 10 000 [67], A partial amino-acid sequence derived from the nucleotide sequence shows considerable homology with subunit c of F-ATPases but not the Mr 16000 proteolipid of V-type ATPases. It is proposed that the proteolipid associated with V-ATPases is a product of a gene that duplicated after the V- and archaeal ATPases had differentiated [67],... 

The properties of the H. salinarium halobium) enzyme are those expected of a V-type ATPase. Polyclonal antibodies prepared against the H. salinarium halobium) ATPase react with the two largest subunits from the ATPases from S. acidocaldarius and beet root tonoplast, but fail to react with the subunits from chloroplast F-ATPase [87]. This result contradicts the observation that polyclonal antiserum against the 3 subunit from S. acidocaldarius, which reacts with various 3 subunits from F-type ATPases, reacts with subunit II from H. saccharovorum and a M, 67000 subunit from the H. salinarium halobium) ATPase [60]. 

The Na K ATPase of the plasma membrane and the Ca " transporters of the sarcoplasmic and endoplasmic reticulums (the SERCA pumps) are examples of P-type ATPases they undergo reversible phosphorylation during their catalytic cycle and are inhibited by the phosphate analog vanadate. F-type ATPase proton pumps (ATP synthases) are central to energy-conserving mechanisms in mitochondria and chloroplasts. V-type ATPases produce gradients of protons across some intracellular membranes, including plant vacuolar membranes. 

Whereas acetylcholine is degraded by a membrane-anchored acetylcholine esterase (ACE) in the synaptic cleft (choline is afterwards taken up presynaptically), the biogenic amines adrenaline, noradrenaline, serotonin, and dopamine are taken up by the presynaptic membrane by transporters (Fig. 3) or by extraneuronal cells in which they are degraded by a catecholamine O-methyltransferase (COMT). These transporter have similar structure and contain 12 transmembrane regions. Once in the presynapse, the neurotransmitters are either degraded by monoamine oxidase (MAO) or taken up by synaptic vesicles. A proton pumping ATPase of the vesicle membrane (V-type ATPase as in plant vacuoles) causes an increase of hydrogen ion concentrations in the vesicles. Uptake of the neurotransmitter serotonin, adrenaline and noradrenaline could be partly achieved either via a diffusion of the free base into the vesicles where they become protonated and concentrated by an "ion trap" mechanism and via specific proton-coupled antiporters. The excitatory amino acids, acetylcholine and ATP cannot diffuse and enter the vesicles via specific transporters. 

Bindseil, K. U., and Zeeck, A. (1994). The chemistry of unusual macrolides, 2. Spectroscopic and biosynthetic investigations of the V-type ATPase inhibitor concanamycin A. Liebigs Ann. Chem. 305-312. 

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