The Cytoplasmic Loop Located between Transmembrane Segments 6 and 7 Controls Activation by Ca2+ of Sarcoplasmic Reticulum Ca2+-ATPase

Menguy, Thierry; Corre, Fabienne; Bouneau, Laurence; Deschamps, Stéphane; Møller, Jesper; Champeil, Philippe; Maire, Marc le; Falson, Pierre

doi:10.1074/jbc.273.32.20134

Cited by 59 publications

(103 citation statements)

References 54 publications

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“…The cytoplasmic loop L6/7 was recently proposed as a possible candidate for the site to which the divalent cations could bind [35]. This observation is in agreement with corresponding findings for the Ca-ATPase [24].…”

Section: Effects Of Divalent Cationssupporting

confidence: 89%

“…All observations presented here, together with the recent proposals from the Ca-ATPase [24] and from 19 kDa membranes [35], support the concept that binding of Na + or K + (or its congeners) to one of the ion sites is competitively blocked by Mg 2+ (or other divalent cations), which is assumed to bind close to the entrance port that is formed at least in part by the cytoplasmic loop L6/7 [3,35]. According to the scheme in Fig.…”

Section: Effects Of Divalent Cationssupporting

confidence: 56%

“…In the first model Tanford et al proposed a so-called jaw-closing model [36] in which by a single-file mechanism the second Ca 2+ binding site is formed "on top" of the first by a structural change of the entrance funnel of the protein. The second, more recent proposal dispenses with the single file mechanism and proposes two sites which are positioned in the protein abreast [24]. Menguy and collaborators suggested that the cytoplasmic loop located between transmembrane segments 6 and 7, L6/7, controls the access to the first and second Ca 2+ binding site, and that this process could be related with the occlusion of the first Ca 2+ by a movement of the L6/7 over the first site, thus opening the second [24].…”

Section: Binding Of Na + In the Absence Of Other Cationsmentioning

confidence: 99%

“…The second, more recent proposal dispenses with the single file mechanism and proposes two sites which are positioned in the protein abreast [24]. Menguy and collaborators suggested that the cytoplasmic loop located between transmembrane segments 6 and 7, L6/7, controls the access to the first and second Ca 2+ binding site, and that this process could be related with the occlusion of the first Ca 2+ by a movement of the L6/7 over the first site, thus opening the second [24]. The recent publication of the crystal structure of the SR Ca-ATPase has proven the side by side binding of Ca 2+ ions, although the loop L6/7 has been given a different assignment as to how it affects Ca 2+ binding [37].…”

Section: Binding Of Na + In the Absence Of Other Cationsmentioning

confidence: 99%

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Ion Selectivity of the Cytoplasmic Binding Sites of the Na,K-ATPase: II. Competition of Various Cations

Schneeberger

Apell

2001

Journal of Membrane Biology

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Abstract.In the E 1 state of the Na,K-ATPase all cations present in the cytoplasm compete for the ion binding sites. The mutual effects of mono-, di-and trivalent cations were investigated by experiments with the electrochromic fluorescent dye RH421. Three sites with significantly different properties could be identified. The most unspecific binding site is able to bind all cations, independent of their valence and size. The large organic cation Br 2 -Titu 3+ is bound with the highest affinity (< M), among the tested divalent cations Ca 2+ binds the strongest, and Na + binds with about the same equilibrium dissociation constant as Mg 2+ (∼0.8 mM). For alkali ions it exhibits binding affinities following the order of Rb + Ӎ K + > Na + > Cs + > Li + . The second type of binding site is specific for monovalent cations, its binding affinity is higher than that of the first type, for Na + ions the equilibrium dissociation constant is < 0.01 mM. Since binding to that site is not electrogenic it has to be close to the cytoplasmic surface. The third site is specific for Na + , no other ions were found to bind, the binding is electrogenic and the equilibrium dissociation constant is 0.2 mM.

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Section: Effects Of Divalent Cationssupporting

confidence: 89%

Section: Effects Of Divalent Cationssupporting

confidence: 56%

Section: Binding Of Na + In the Absence Of Other Cationsmentioning

confidence: 99%

Section: Binding Of Na + In the Absence Of Other Cationsmentioning

confidence: 99%

See 2 more Smart Citations

Ion Selectivity of the Cytoplasmic Binding Sites of the Na,K-ATPase: II. Competition of Various Cations

Schneeberger

Apell

2001

Journal of Membrane Biology

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“…An alternative explanation to this single-file process has been recently proposed by Menguy et al (1998). They present evidence that the cytoplasmic loop between transmembrane segments M6 and M7, with its negatively charged amino acids is involved in binding of the first Ca 2+ ion and, upon interaction with the first Ca 2+ , access to the second binding site within the transmembrane domains of the protein becomes possible.…”

Section: Refinement Of a Mechanistic Modelmentioning

confidence: 92%

Electrogenic Partial Reactions of the SR-Ca-ATPase Investigated by a Fluorescence Method

Butscher

Roudná

Apell

1999

Journal of Membrane Biology

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Abstract.A fluorescence method was adapted to investigate active ion transport in membrane preparations of the SR-Ca-ATPase. The styryl dye RH421 previously used to investigate the Na,K-ATPase was replaced by an analogue, 2BITC, to obtain optimized fluorescence changes upon substrate-induced partial reactions. Assuming changes of the local electric field to be the source of fluorescence changes that are produced by uptake/ release or by movement of ions inside the protein, 2BITC allowed the determination of electrogenic partial reactions in the pump cycle. It was found that Ca 2+ binding on the cytoplasmic and on the lumenal side of the pump is electrogenic while phosphorylation and conformational transition showed only minor electrogenicity. Ca 2+ equilibrium titration experiments at pH 7.2 in the two major conformations of the protein indicated cooperative binding of two Ca 2+ ions in state E 1 with an apparent half-saturation concentration, K M of 600 nM. In state P-E 2 two K M values, 5 M and 2.2 mM, were determined and are in fair agreement with published data. From Ca 2+ titrations in buffers with various pH and from pH titrations in P-E 2 , it could be demonstrated that H + binding is electrogenic and that Ca 2+ and H + compete for the same binding site(s). Tharpsigargin-induced inhibition of the Ca-ATPase led to a state with a specific fluorescence level comparable to that of state E 1 with unoccupied ion sites, independent of the buffer composition.

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Molecular dynamics simulation exploration of cooperative migration mechanism of calcium ions in sarcoplasmic reticulum Ca²⁺‐ATPase

Huang

2009

J Comput Chem

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Calcium ATPase is a member of the P-type ATPase, and it pumps calcium ions from the cytoplasm into the reticulum against a concentration gradient. Several X-ray structures of different conformations have been solved in recent years, providing basis for elucidating the active transport mechanism of Ca2+ ions. In this work, molecular dynamics (MD) simulations were performed at atomic level to investigate the dynamical process of calcium ions moving from the outer mouth of the protein to their binding sites. Five initial locations of Ca2+ ions were considered, and the simulations lasted for 2 or 6 ns, respectively. Specific pathways leading to the binding sites and large structural rearrangements around binding sites caused by uptake of calcium ions were identified. A cooperative binding mechanism was observed from our simulation. Firstly, the first Ca2+ ion binds to site I, and then, the second Ca2+ ion approaches. The interactions between the second Ca2+ and the residues around site I disturb the binding state of site I and weaken its binding ability for the first bound Ca2+. Because of the electrostatic repulsion of the second Ca2+ and the electrostatic attraction of site II, the first bound Ca2+ shifts from site I to site II. Concertedly, the second Ca2+ binds to site I, forming a binding state with two Ca2+ ions, one at site I and the other at site II. Both of Glu908 and Asp800 coordinate with the two Ca2+ ions simultaneously during the concerted binding process, which is believed to be the hinge to achieve the concerted binding. In our simulations, four amino acid residues that serve as the channel to link the outer mouth and the binding sites during the binding process were recognized, namely Tyr837, Tyr763, Asn911, and Ser767. The analyses regarding the activity of the proteins via mutations of some key residues also supported our cooperative mechanism.

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The Cytoplasmic Loop Located between Transmembrane Segments 6 and 7 Controls Activation by Ca2+ of Sarcoplasmic Reticulum Ca2+-ATPase

Cited by 59 publications

References 54 publications

Ion Selectivity of the Cytoplasmic Binding Sites of the Na,K-ATPase: II. Competition of Various Cations

Ion Selectivity of the Cytoplasmic Binding Sites of the Na,K-ATPase: II. Competition of Various Cations

Electrogenic Partial Reactions of the SR-Ca-ATPase Investigated by a Fluorescence Method

Molecular dynamics simulation exploration of cooperative migration mechanism of calcium ions in sarcoplasmic reticulum Ca²⁺‐ATPase

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The Cytoplasmic Loop Located between Transmembrane Segments 6 and 7 Controls Activation by Ca2+ of Sarcoplasmic Reticulum Ca2+-ATPase

Cited by 59 publications

References 54 publications

Ion Selectivity of the Cytoplasmic Binding Sites of the Na,K-ATPase: II. Competition of Various Cations

Ion Selectivity of the Cytoplasmic Binding Sites of the Na,K-ATPase: II. Competition of Various Cations

Electrogenic Partial Reactions of the SR-Ca-ATPase Investigated by a Fluorescence Method

Molecular dynamics simulation exploration of cooperative migration mechanism of calcium ions in sarcoplasmic reticulum Ca2+‐ATPase

Contact Info

Product

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About

Molecular dynamics simulation exploration of cooperative migration mechanism of calcium ions in sarcoplasmic reticulum Ca²⁺‐ATPase