Role of magnesium in the relaxation of myofibrils

Weber, Annemarie; Herz, Ruth; Reiss, I.

doi:10.1021/bi00834a005

Cited by 109 publications

(92 citation statements)

References 34 publications

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“…In fact, the experimental points obtained at neutral pH were satisfactorily fitted by the use of empirical equations assuming two interacting binding-site domains and were consistent with the notion that two calcium ions are transported per enzyme cycle (13,14). With the more elaborate analysis of the present paper, using a different pCa scale, we find that two interacting domains are not sufficient.…”

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confidence: 82%

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Equilibrium cooperative binding of calcium and protons by sarcoplasmic reticulum ATPase.

Hill¹,

Inesi²

1982

Proc. Natl. Acad. Sci. U.S.A.

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The cooperative equilibrium binding of Ca2+ by sarcoplasmic reticulum ATPase, as modulated by pH, is analyzed by statistical mechanical treatment of a theoretical model. The model consists offour equivalent subunits, in the form ofa square, with nearest-neighbor interactions. Each subunit has one site for binding of one Ca2+ or one proton, but not both. Binding ofeither ligand on a subunit induces a conformational change in the subunit that alters its interaction with its two neighbors. The model gives good agreement with experimental binding data. It should prove useful as a starting point in the analysis of steady-state ATPase activity as a function of Ca2+ and H+ concentrations.Calcium binding is an absolute requirement for activation of sarcoplasmic reticulum (SR) ATPase. Of various classes of binding sites found in SR vesicles (1-4), only a class of high affinity sites is specifically involved in enzyme activation and calcium transport (5-7). Occupation of these sites is accompanied by protein (ATPase) conformational changes, as shown with various spectroscopic methods (8-11).Under equilibrium conditions, the Ca2+ concentration dependence of binding and of Ca2+-induced conformational changes are identical, and the shape ofthe Ca2O titration curves suggests a cooperative binding mechanism (12). In fact, the experimental points obtained at neutral pH were satisfactorily fitted by the use of empirical equations assuming two interacting binding-site domains and were consistent with the notion that two calcium ions are transported per enzyme cycle (13,14). With the more elaborate analysis of the present paper, using a different pCa scale, we find that two interacting domains are not sufficient.Subsequent studies (15) A family of curves displaying calcium binding to SR vesicles as a function of molar Ca2+(c1) and H+(c2) concentrations is shown in Fig. 1. Most of these data were presented previously (12,15). The two different values for maximal binding mentioned in the figure legend reflect the different specific activity of SR preparations over a 3-yr period. The fractional saturation 6 is used as ordinate in the figure.THE MODEL AND ITS PROPERTIES The Ca2+ binding curves in Fig. 1 The publication costs ofthis article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.

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confidence: 82%

“…In the above special case (b = 0), it is not difficult to obtain an analytical expression for the slope at a = 1 or 0 = 1/2: dO/dln a -dO/dln c1 = (1 + y)/(l + 6y + y2) (0= 1/2) [14] This has the value 1/4 when y = I (no cooperativity) and the value 1 when y = 0 (maximum positive cooperativity). When y -* 0, (2wo, -woo wl,)/kT -X00 (Eq.…”

mentioning

confidence: 99%

Equilibrium cooperative binding of calcium and protons by sarcoplasmic reticulum ATPase.

Hill¹,

Inesi²

1982

Proc. Natl. Acad. Sci. U.S.A.

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“…In other words, under the conditions, under which the calcium fluxes and NTP-NDP exchange reaction are stimulated, the orthophosphate incorporation into NTP is completely suppressed. These experimental results allow to establish the sequence of two essential steps in the reaction chain of calcium translocation for which the following scheme has tentatively been proposed [1][2][3][4][5][6][7][8] indicate that the phosphorylated carrier releases the calcium to the internal space of the vesicles before the bound phosphate is lost. If the phosphorylated enzyme lost the phosphate simultaneously with the calcium or even before it, one should expect an activation of orthophosphate incorporation into the NTP fraction when the calcium exchange is enhanced.…”

Section: Resultsmentioning

confidence: 99%

“…In this respect the sarcoplasmic membrane proved to be superior to most other membranes with transport activity. On the basis of such studies, a number of reaction mechanisms of the sarcoplasmic calcium pump were proposed by several authors with more or less experimental support [1][2][3][4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Possible functional states of the enzyme of the sarcoplasmic calcium pump

Makinose

1973

FEBS Letters

118

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“…Protein was precipitated from the hemolysate with acetone containing 1 Vo of 1 M HCl before the measurement. SDS-PAGE was performed both according to Laemmli [18] or to Weber and Osborn [19], using a 15% gel.…”

Section: Analytical Proceduresmentioning

confidence: 99%

Nucleoside diphosphate kinase from human erythrocytes: Purification, molecular mass and subunit structure

Presecan¹,

Vonica²,

Lascu³

1989

FEBS Letters

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A new procedure for the purification of nucleoside diphosphate kinase from human erythrocytes is described. The enzyme (105 kDa by gel filtration) is made up of two different kinds of subunits (19.0 and 20.5 kDa), both displaying enzymatic activity. The probable subunit structure of the enzyme is hexameric. The discrepancies related to earlier work are discussed.Nucleoside diphosphate kinase; Affinity chromatography; Subunit structure; (Human erythrocyte)

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Role of magnesium in the relaxation of myofibrils

Cited by 109 publications

References 34 publications

Equilibrium cooperative binding of calcium and protons by sarcoplasmic reticulum ATPase.

Equilibrium cooperative binding of calcium and protons by sarcoplasmic reticulum ATPase.

Possible functional states of the enzyme of the sarcoplasmic calcium pump

Nucleoside diphosphate kinase from human erythrocytes: Purification, molecular mass and subunit structure

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