+ Site Statistics
References:
54,258,434
Abstracts:
29,560,870
PMIDs:
28,072,757
+ Search Articles
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ PDF Full Text
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Translate
+ Recently Requested

Calcium and proton dependence of sarcoplasmic reticulum ATPase



Calcium and proton dependence of sarcoplasmic reticulum ATPase



Biophysical Journal 44(2): 271-280



The influence of Ca2+ and H+ concentrations on the sequential reactions of the ATPase cycle was studied by a series of pre-steady state and steady state experiments with sarcoplasmic reticulum vesicles. It is shown that H+ competition with calcium binding results in a reduced population of activated enzyme, which is manifested by a lower level of phosphorylated enzyme intermediate following addition of ATP. Further effects of Ca2+ and H+ are demonstrated on the progression of the phosphoenzyme through the reaction cycle and on the final hydrolytic cleavage of Pi. The overall dependence of steady state ATP flux on Ca2+ and H+ concentrations in leaky vesicles is expressed by a series of curves showing that as the H+ concentration is raised higher Ca2+ concentrations are required to obtain half-maximal ATP fluxes. At saturating Ca2+, maximal ATP fluxes are observed at an intermediate H+ concentration (pH 7.2), while lower levels are obtained as the H+ concentration is reduced (to pH 8) or increased (to pH 6). A preliminary model is then proposed based on the presence of two interacting domains permitting competitive binding of Ca2+ or H+, per each catalytic site undergoing phosphorylation by ATP. The model considers three main states and thirteen substates (depending on the occupancy of the binding sites in each state by Ca2+, H+, or neither) in the progression of the ATP cycle, coupled to transport of Ca2+ and counter transport of H+ in leaky vesicles. Considering the preliminary nature of the model and the experimental scatter, a rather satisfactory agreement is noted between a family of curves generated by theoretical analysis and the ATP flux curves obtained experimentally.

(PDF emailed within 0-6 h: $19.90)

Accession: 004866710

Download citation: RISBibTeXText

PMID: 6317076

DOI: 10.1016/S0006-3495(83)84299-4


Related references

Proton concentration dependence of calcium induced changes of intrinsic fluorescence in sarcoplasmic reticulum atpase. Biophysical Journal 41(2 PART 2): 170A, 1983

Proton nmr studies on nucleotide binding to the sarcoplasmic reticulum calcium atpase ec 3.6.1.3 determination of the conformations of bound nucleotides by the measurement of proton proton transferred nuclear overhauser enhancements. European Journal of Biochemistry 128(1): 113-118, 1982

Two types of proton-modulated calcium binding in the sarcoplasmic reticulum Ca(2+)-ATPase. I. A model of two different conformations of chemically equivalent ATPase molecules. Journal of Biological Chemistry 269(49): 30818-30821, 1994

The reconstituted calcium atpase from sarcoplasmic reticulum mediates calcium proton exchange. Biophysical Journal 45(2 PART 2): 189A, 1984

Two types of proton-modulated calcium binding in the sarcoplasmic reticulum Ca(2+)-ATPase. II. Characteristics of their calcium bindings. Journal of Biological Chemistry 269(49): 30822-7, 1994

The oligomeric structure of the proton atpase from neurospora crassa plasma membranes evidence from radiation inactivation and comparison with the calcium atpase of sarcoplasmic reticulum. Federation Proceedings 44(3): 612, 1985

Cooperative proton and calcium binding by sarcoplasmic reticulum ATPase. Febs Letters 308(1): 59-61, 1992

Chemical modification of the calcium ion dependent atpase ec 3.6.1.3 of sarcoplasmic reticulum from skeletal muscle part 1 binding of n ethyl maleimide to sarcoplasmic reticulum evidence for sulfhydryl groups in the active site of atpase and for conformational changes induced by adp and atp. Journal of Biochemistry 79(3): 649-654, 1976

Evidence for proton countertransport by the sarcoplasmic reticulum calcium atpase during calcium transport in reconstituted proteoliposomes with low ionic permeability. Journal of Biological Chemistry 265(32): 19524-19534, 1990

The ph dependence of the calcium magnesium atpase of sarcoplasmic reticulum evidence that the calcium ion translocator bears a doubly negative charge. Journal of Membrane Biology 74(1): 25-40, 1983

Calcium dependence during single-cycle catalysis of the sarcoplasmic reticulum ATPase. Journal of Biological Chemistry 263(24): 11786-11791, 1988

Effect of ph on calcium ion dependence of dog cardiac sarcoplasmic reticulum atpase activity. Journal of Molecular & Cellular Cardiology 17(5): 505-510, 1985

Dependence of the calcium induced release from the sarcoplasmic reticulum of skinned skeletal muscle fibers from the frog semitendinosus on the rate of change of free calcium concentration at the outer surface of the sarcoplasmic reticulum. Journal of Physiology (Cambridge) 353: 56P, 1984

Calcium binding to sarcoplasmic reticulum ATPase revisited Influence of proton and magnesium on its cooperativity. Biophysical Journal 64(2 PART 2): A333, 1993

Temperature dependence of molecular dynamics and calcium-ATPase activity in sarcoplasmic reticulum. Cossins, A R Portland Press Proceedings; Temperature adaptation of biological membranes 1-12, 1994