scholarly journals AlF4- reversibly inhibits ‘P’-type cation-transport ATPases, possibly by interacting with the phosphate-binding site of the ATPase

1988 ◽  
Vol 253 (3) ◽  
pp. 827-833 ◽  
Author(s):  
L Missiaen ◽  
F Wuytack ◽  
H De Smedt ◽  
M Vrolix ◽  
R Casteels
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Binding Site ◽  
G Proteins ◽  
Time Course ◽  
Cation Transport ◽  
Phosphate Binding ◽  
Intact Cells ◽  
Nitrophenyl Phosphate ◽  
Transport Atpases ◽  
P Type

The only known cellular action of AlF4- is to stimulate the G-proteins. The aim of the present work is to demonstrate that AlF4- also inhibits ‘P’-type cation-transport ATPases. NaF plus AlCl3 completely and reversibly inhibits the activity of the purified (Na+ + K+)-ATPase (Na+- and K+-activated ATPase) and of the purified plasmalemmal (Ca2+ + Mg2+)-ATPase (Ca2+-stimulated and Mg2+-dependent ATPase). It partially inhibits the activity of the sarcoplasmic-reticulum (Ca2+ + Mg2+)-ATPase, whereas it does not affect the mitochondrial H+-transporting ATPase. The inhibitory substances are neither F- nor Al3+ but rather fluoroaluminate complexes. Because AlF4- still inhibits the ATPase in the presence of guanosine 5′-[beta-thio]diphosphate, and because guanosine 5′-[beta gamma-imido]triphosphate does not inhibit the ATPase, it is unlikely that the inhibition could be due to the activation of an unknown G-protein. The time course of inhibition and the concentrations of NaF and AlCl3 required for this inhibition differ for the different ATPases. AlF4- inhibits the (Na+ + K+)-ATPase and the plasmalemmal (Ca2+ + Mg2+)-ATPase noncompetitively with respect to ATP and to their respective cationic substrates, Na+ and Ca2+. AlF4- probably binds to the phosphate-binding site of the ATPase, as the Ki for inhibition of the (Na+ + K+)-ATPase and of the plasmalemmal (Ca2+ + Mg2+)-ATPase is shifted in the presence of respectively 5 and 50 mM-Pi to higher concentrations of NaF. Moreover, AlF4- inhibits the K+-activated p-nitrophenylphosphatase of the (Na+ + K+)-ATPase competitively with respect to p-nitrophenyl phosphate. This AlF4- –induced inhibition of ‘P’-type cation-transport ATPases warns us against explaining all the effects of AlF4- on intact cells by an activation of G-proteins.

scholarly journals The nucleotide-binding domain of the Zn2+-transporting P-type ATPase from Escherichia coli carries a glycine motif that may be involved in binding of ATP

2004 ◽  
Vol 377 (1) ◽  
pp. 95-105 ◽  
Author(s):  
Juha OKKERI ◽  
Liisa LAAKKONEN ◽  
Tuomas HALTIA
Keyword(s):  
Escherichia Coli ◽  
Sarcoplasmic Reticulum ◽  
Binding Site ◽  
Molecular Model ◽  
Nucleotide Binding ◽  
Atp Binding ◽  
Atp Binding Site ◽  
Disease Mutations ◽  
Disease Protein ◽  
P Type

In P-type ATPases, the nucleotide-binding (N) domain is located in the middle of the sequence which folds into the phosphorylation (P) domain. The N domain of ZntA, a Zn2+-translocating P-type ATPase from Escherichia coli, is approx. 13% identical with the N domain of sarcoplasmic reticulum Ca2+-ATPase. None of the Ca2+-ATPase residues involved in binding of ATP are found in ZntA. However, the sequence G503SGIEAQV in the N domain of ZntA resembles the motif GxGxxG, which forms part of the ATP-binding site in protein kinases. This motif is also found in Wilson disease protein where several disease mutations cluster in it. In the present work, we have made a set of disease mutation analogues, including the mutants G503S (Gly503→Ser), G505R and A508F of ZntA. At low [ATP], these mutant ATPases are poorly phosphorylated. The phosphorylation defect of the mutants G503S and G505R can, however, be partially (G503S) or fully (G505R) compensated for by using a higher [ATP], suggesting that these mutations lower the affinity for ATP. In all three mutant ATPases, phosphorylation by Pi has become less sensitive to the presence of ATP, also consistent with the proposal that the Gly503 motif plays a role in ATP binding. In order to test this hypothesis, we have modelled the N domain of ZntA using the sarcoplasmic reticulum Ca2+-ATPase structure as a template. In the model, the Gly503 motif, as well as the residues Glu470 and His475, are located in the proximity of the ATP-binding site. In conclusion, the mutagenesis data and the molecular model are consistent with the idea that the two loops carrying the residues Glu470, His475, Gly503 and Gly505 play a role in ATP binding and activation.

scholarly journals Identification of the Mg2+-binding site in the P-type ATPase and phosphatase members of the HAD (haloacid dehalogenase) superfamily by structural similarity to the response regulator protein CheY

1999 ◽  
Vol 339 (2) ◽  
pp. 223-226 ◽  
Author(s):  
Ivo S. RIDDER ◽  
Bauke W. DIJKSTRA
Keyword(s):  
Binding Site ◽  
Response Regulator ◽  
Three Dimensional ◽  
Structural Similarity ◽  
Dimensional Structure ◽  
Phosphate Binding ◽  
Haloacid Dehalogenase ◽  
Regulator Protein ◽  
P Type ◽  
Response Regulator Protein

The large HAD (haloacid dehalogenase) superfamily of hydrolases comprises P-type ATPases, phosphatases, epoxide hydrolases and l-2-haloacid dehalogenases. A comparison of the three-dimensional structure of l-2-haloacid dehalogenase with that of the response regulator protein CheY allowed the assignment of a conserved pair of aspartate residues as the Mg2+-binding site in the P-type ATPase and phosphatase members of the superfamily. From the resulting model of the active site, a conserved serine/threonine residue is suggested to be involved in phosphate binding, and a mechanism comprising a phosphoaspartate intermediate is postulated.

Ca2+ binding and translocation by the sarcoplasmic reticulum ATPase: Functional and structural considerations

1995 ◽  
Vol 15 (5) ◽  
pp. 327-339 ◽  
Author(s):  
Giuseppe Inesi ◽  
Li Chen ◽  
Carlota Sumbilla ◽  
David Lewis ◽  
Mary E. Kirtley
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Ions ◽  
Binding Sites ◽  
Cation Transport ◽  
Cooperative Binding ◽  
Experimental Systems ◽  
Highly Sensitive ◽  
Membrane Bound ◽  
Transport Atpases ◽  
Globular Head

Three experimental systems are described including sarcoplasmic reticulum (SR) vesicles, reconstituted proteoliposomes, and recombinant protein obtained by gene transfer and expression in foreign cells. It is shown that the Ca2+ ATPase of sarcoplasmic reticulum (SR) includes an extramembranous globular head which is connected through a stalk to a membrane bound region. Cooperative binding of two calcium ions occurs sequentially, within a channel formed by four clustered helices within the membrane bound region. Destabilization of the helical cluster is produced following enzyme phosphorylation by ATP at the catalytic site in the extramembranous region. The affinity and orientation of the Ca2+ binding site are thereby changed, permitting vectorial dissociation of bound Ca2+ against a concentration gradient. A long range linkage between phosphorylation and Ca2+ binding sites is provided by an intervening peptide segment that retains high homology in cation transport ATPases, and whose function is highly sensitive to mutational perturbations.

Mechanism of Ca2+ transport by Ca2+-Mg2+-ATPase pump: analysis of major states and pathways

1983 ◽  
Vol 244 (1) ◽  
pp. G3-G12 ◽  
Author(s):  
D. H. Haynes
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Binding Site ◽  
Random Order ◽  
Product Inhibition ◽  
Phosphate Binding ◽  
Stoichiometric Amount ◽  
Transport Cycle ◽  
Adp Release ◽  
Normal Transport ◽  
A Charge

Mechanistic studies of Ca2+ transport by the Ca2+-Mg2+-ATPase of skeletal sarcoplasmic reticulum are reviewed, and a unifying model is proposed. The significant steps in the transport cycle are modeled in terms of occupation and disposition of three binding sites on the enzyme: a) two translocation sites capable of binding to Ca2+ or a charge-stoichiometric amount of alkali cation (M+) or H+, b) an ATP-ADP-binding site, and c) a phosphorylation or phosphate-binding site. The normal transport cycle is characterized as the following sequence of steps: a) binding of two Ca2+ and Mg-ATP to external sites with high affinity and random order, b) enzyme phosphorylation, c) inward translocation of the Ca2+-laden sites, d) Ca2+ release to the sarcoplasmic reticulum lumen and ADP release to the external medium (random order), e) binding of Mg2+ or a charge-stoichiometric amount of K+ plus H+ to the translocators, f) dephosphorylation, g) the return of the K+- and H+-laden translocators to the outside, and h) dissociation of K+ and H+ from the translocator and completion of the cycle with step a. The enzyme is characterized as a Ca2+-K+ plus H+ countertransporter. The K+ plus H+ remove Ca2+ from the inwardly oriented translocator, thereby relieving a product inhibition and increasing the rate of enzyme dephosphorylation.

Effects of the Ca2+ sensitizer EMD 57033 on intracellular Ca2+ in rat ventricular myocytes: relevance to arrhythmogenesis during positive inotropy

2000 ◽  
Vol 99 (6) ◽  
pp. 547-554 ◽  
Author(s):  
Makoto KAWAI ◽  
John A. LEE ◽  
Clive H. ORCHARD
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Rise Time ◽  
Time Course ◽  
Ventricular Myocytes ◽  
Troponin C ◽  
Intact Cells ◽  
Positive Inotropy ◽  
Rat Ventricular Myocytes ◽  
Cross Bridge ◽  
Butanedione Monoxime

We have investigated the effects of the calcium-sensitizing inotropic agent EMD 57033 on Ca2+ handling in intact and skinned rat ventricular myocytes. Intracellular Ca2+ was monitored using fura 2. Myocytes were saponin-skinned, allowing study of sarcoplasmic reticulum (SR) function. In intact myocytes EMD 57033 (1–10 µmol/l) produced a concentration-dependent decrease in the amplitude of the Ca2+ transient and prolonged its declining phase, but had no effect on the rise time. In skinned myocytes, the amplitude of spontaneous Ca2+ release from the SR was decreased by EMD 57033 (5 and 10 µmol/l), although this agent had no significant effect on the frequency of spontaneous Ca2+ release. In the presence of the cross-bridge inhibitor 2,3-butanedione monoxime (5 mmol/l), or in a low bathing Ca2+ concentration (1 mmol/l), EMD 57033 (10 µmol/l) had smaller effects on both the amplitude and time course of the Ca2+ transient in intact cells than in the absence of 2,3-butanedione monoxime or in the presence of 2 and 5 mmol/l Ca2+ respectively. These data suggest that the effects of EMD 57033 on Ca2+ are due to changes in Ca2+ binding to troponin C, secondary to cross-bridge formation. Thus, during positive inotropy, EMD 57033 is unlikely to provoke arrhythmias due to effects on SR Ca2+ handling. In intact cells, its effects on Ca2+ handling would be expected to protect against arrhythmias.

Phosphate Binding to Isolated Chloroplast Coupling Factor (CF1)

1988 ◽  
Vol 43 (3-4) ◽  
pp. 213-218 ◽  
Author(s):  
Bernhard Huchzermeyer
Keyword(s):  
Atpase Activity ◽  
Binding Site ◽  
Inorganic Phosphate ◽  
Coupling Factor ◽  
Binding Domain ◽  
Atp Binding ◽  
Phosphate Binding ◽  
Chloroplast Coupling Factor ◽  
Single Binding Site ◽  
Site Binding

A single binding site for phosphate was found on isolated chloroplast coupling factor in the absence of nucleotides. In our experiments the phosphate binding site showed a Kd of 170 μᴍ. We did not observe any differences whether the ATPase activity of CF] had been activated or not. If the enzyme was incubated with [γ-32P]ATP the amount of 32P bound per CF1 depended on the pretreatment of the enzyme: In the presence of ADP no ATP or phosphate was bound to CF,. After activation of ATPase activity one mol of ATP per mol CF, was rapidly bound and hydrolyzed while there was a slowly occurring binding of another phosphate without concomitant nucleotide binding. We conclude that there are two different types of phosphate binding observed in our experiments: 1) Inorganic phosphate can be bound by one catalytic site per mol of CF1 2) The γ-phosphate of ATP is able to bind to an ATP binding domain of the enzyme if this domain can exchange substrates with the incubation medium. This ATP binding domain appears to differ from the site binding inorganic phosphate, because at least a portion of the coupling factor contains more than one labelled phosphate during our ATPase tests.

Nicotinic receptor binding site probed with unnatural amino acid incorporation in intact cells

Science ◽  
1995 ◽  
Vol 268 (5209) ◽  
pp. 439-442 ◽  
Author(s):  
M. Nowak ◽  
P. Kearney ◽  
Sampson ◽  
M. Saks ◽  
C. Labarca ◽  
...  
Keyword(s):  
Amino Acid ◽  
Binding Site ◽  
Receptor Binding ◽  
Nicotinic Receptor ◽  
Unnatural Amino Acid ◽  
Amino Acid Incorporation ◽  
Receptor Binding Site ◽  
Intact Cells ◽  
Acid Incorporation

Location of N-cyclohexyl-N'-(4-dimethyl-amino-alpha-naphthyl)carbodiimide-binding site in sarcoplasmic reticulum Ca2+-transporting ATPase

1998 ◽  
Vol 253 (1) ◽  
pp. 339-344 ◽  
Author(s):  
Isabel Velasco-Guillen ◽  
Senena Corbalan-Garcia ◽  
Juan C. Gomez-Fernandez ◽  
Jose A. Teruel
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Binding Site
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