Transport ATPases

Ion transporting ATPases that become autophosphory-lated by the terminal phosphate group of ATP during the ion transporting process... 

Transmembrane Signaling Transport ATPase Transporter Transposon Transverse Tubule Triazenes... 

Janik F, Wolf HU. 1992. The Ca2-i-transport-atpase of human erythrocytes as an in vitro toxicity test system - acute effects of some chlorinated compounds. J Appl Toxicol 12(5) 351-358. 

The Ca transport ATPases of sarco(endo)-plasmic reticulum and plasma membranes... 

The Ca transport ATPase of sarcoplasmic reticulum is an intrinsic membrane protein of 110 kDa [8-11] that controls the distribution of intracellular Ca by ATP-dependent translocation of Ca " ions from the cytoplasm into the lumen of the sarcoplasmic reticulum [12-16],... 

The Ca transport ATPase of the surface membrane is a Ca -calmodulin-dependent enzyme of approximately 138-kDa mass that is structurally distinct from the sarcoplasmic reticulum Ca -ATPase, but shares with it some similarities in the mechanism of Ca translocation [2,3,34]. In both enzymes the Ca -dependent phosphorylation of an aspartyl-carboxyl-group by ATP leads to the formation of an acyl phosphate intermediate that provides the coupling between ATP hydrolysis and Ca translocation. 

Our discussion here will concentrate on the various forms of the Ca " transport ATPases that occur in the sarcoplasmic reticulum of muscle cells of diverse fiber types and in the endoplasmic reticulum of nonmuscle cells (SERCA). The structure of these enzymes will be compared with the Ca transport ATPases of surface membranes (PMCA) [3,29-32,34] and with other ATP-dependent ion pumps that transport Na, K, andH [46,50-52]. 

The Ccr transport ATPases of sarco(endo)plasmic reticulum (SERCA)... 

The molecular weights of all SERCA-type Ca " transport ATPases are in the range of 100-110 kDa. Their N-terminal sequences are similar Met-Glu-X(Ala, Asn, Glu, Asp)-X (Ala, Gly, He). The Met-Glu-X-X sequence serves as a signal for the acetylation of N-terminal methionine both in soluble and in membrane proteins [71,72]. 

Hydropathy plots [133] of the slow and fast Ca -ATPase isoenzymes are nearly identical and provide unambiguous prediction of four of the proposed transmembrane segments (Mi, M2, M3 and M4) [8,11]. Similar hydropathy plots were also obtained for other closely related cation transporting ATPases [31,46,47,134]. 

Although the sequence identity averaged over the whole length of the molecule is generally low among different P-type ion transport ATPases, the conserved sequences around the phosphate acceptor aspartyl group and in the ATP binding domain are well preserved [30,32,46]. Structure predictions based on the hydropathy plots... 

Blasie and his colleagues have determined the separate profile structures of the lipid bilayer and of the Ca transport ATPase molecule within the sarcoplasmic reticulum membrane to 11 A resolution by a combination of X-ray and neutron diffraction techniques [128,140,187-199]. 

Reliable information about the transmembrane topology of ion transport ATPases can be obtained only by a combination of predictions based on amino acid sequence... 

Effects of Allelochemlcals on ATPases. Several flavonoid compounds inhibit ATPase activity that is associated with mineral absorption. Phloretin and quercetin (100 pM) inhibited the plasma membrane ATPase Isolated from oat roots (33). The naphthoquinone juglone was inhibitory also. However, neither ferulic acid nor salicylic acid inhibited the ATPase. Additional research has shown that even at 10 mM salicylic acid inhibits ATPase activity only 10-15% (49). This lack of activity by salicylic acid was substantiated with the plasma membrane ATPase Isolated from Neurospora crassa (50) however, the flavonols fisetln, morin, myricetin, quercetin, and rutin were inhibitory to the Neurospora ATPase. Flavonoids inhibited the transport ATPases of several animal systems also (51-53). Thus, it appears that flavonoids but not phenolic acids might affect mineral transport by inhibiting ATPase enzymes. 

PS Reinach, N Holmbeg, R Chiesa. (1991). Identification of calmodulin-sensitive Ca2+-transporting ATPase in the plasma membrane of bovine corneal epithelial cell. Biochim Biophys Acta 1068 1-8. 

The organization of lipids around the plasma membrane Ca2+-transport ATPase of erythrocytes has been also determined by FRET. Taking advantage of the intrinsic fluorescence of the ATPase due to tryptophan residues and labeling different types of lipids with pyrene, it was demonstrated that the transporter is preferentially surrounded by negatively charged lipids such as phosphoinositides [167],... 

Verbist, J., Gadella, T. W. J., Raeymaekers, L., Wuytack, F., Wirtz, K. W. A. and Casteels, R. (1991). Phosphoinositide-protein Interactions of the plasma-membrane Ca2+-transport ATPase as revealed by fluorescence energy-transfer. Biochim. Biophys. Acta 1063, 1-6. 

Figure 7.32 Apo form of metal binding domain 4 of Menkes copper-transporting ATPase described in reference 133 (PDB 1AW0). Visualized using Wavefunction, Inc. Spartan 02 for Windows . See text for visualization details. Printed with permission of Wavefunction, Inc., Irvine, CA. (See color plate.)...

Inesi G, Sagara Y 1994 Specific inhibitors of intracellular Ca2+ transport ATPases. J Membr Biol... 

Raeymaekers L, Wuytack F 1996 Calcium Pumps. In Barany M (ed) Biochemistry of smooth muscle contraction. Academic Press, New York, p 241-253 Shull GE 2000 Gene knockout studies of Ca2+-transporting ATPases. Eur J Biochem 267 5284-5290... 

EXPORT FROM THE CELL TO THE BLOOD BY PRIMARY TRANSPORT ATPASES... 

Repacking of the transmembrane domains of P-glycoprotein during the transport ATPase cycle. EMBO Journal, 20, 5615-5625. 

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