Mitochondrial ATP Synthase Catalytic Mechanism: A Novel Visual Comparative Structural Approach Emphasizes Pivotal Roles for Mg2+ and P-Loop Residues in Making ATP
Department of Biological Chemistry, The Johns Hopkins University, School of Medicine, 725 North Wolfe Street, Baltimore, Maryland 21205-2185, United States. Biochemistry
(Impact Factor: 3.02).
02/2012; 51(7):1532-46. DOI: 10.1021/bi201595v
The mitochondrial ATP synthase (F(o)F(1)) is one of the most abundant, important, and complex enzymes found in animals and humans. In earlier studies, we used the photosensitive phosphate analogue vanadate (V(i)) to study the enzyme's mechanism in the transition state. Significantly, these studies showed that Mg(2+) plays an important role in transition state formation during ATP synthesis. Additionally, in both MgADP·V(i)-F(1) and MgV(i)-F(1) complexes, photoactivation of orthovanadate (V(i)) induced cleavage at the third residue within the P-loop (GGAGVGKT), i.e., βA158, suggesting its proximity to the γ-phosphate during transition state formation. However, despite our recent release of the F(1)-ATPase structure containing V(i), the structural details regarding the role of Mg(2+) have remained elusive. Therefore, in this study, we sought to improve our understanding of the essential role of Mg(2+) during transition state formation. We utilized Protein Data Bank structural data representing different conformational intermediates of key steps in ATP synthesis to assemble a database of positional relationships between landmark residues of the catalytic site and the bound ligand. Applying novel bioinformatics methods, we combined the resulting interatomic spatial data with an animated model of the catalytic site to visualize the exact nature of the changes in these positional relationships during ATP synthesis. The results of these studies reported here show that the absence of Mg(2+) results in migration of inorganic phosphate (P(i)) from βA158 to a more medial position in the P-loop binding pocket, thereby disrupting essential placement and orientation of the P(i) needed to form the transition state structure and therefore MgATP.
Available from: Matthew Brain
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ABSTRACT: To describe magnesium flux and serum concentrations in ICU patients receiving continuous venovenous haemodiafiltration (CVVHDF).
Samples were collected from 22 CVVHDF circuits using citrate anticoagulation solutions (Prismocitrate 10/2 and Prism0cal) and from 26 circuits using Hemosol B0 and heparin anticoagulation. CVVHDF prescription, magnesium supplementation and anticoagulation choice was by the treating intensivist. We analysed 334 sample sets consisting of arterial, prefilter and postfilter blood and effluent. Magnesium loss was calculated from an equation for conservation of mass, and arterial magnesium concentration was described by an equation for exponential decay.
Using flow rates typical of adults receiving CVVHDF, we determined a median half-life for arterial magnesium concentration to decay to a new steady state of 4.73 hours (interquartile range [IQR], 3.73-7.32 hours). Median arterial magnesium concentration was 0.88mmol/L (IQR, 0.83-0.97mmol/L) in the heparin group and 0.79mmol/L (IQR, 0.69-0.91mmol/L) in the citrate group. Arterial magnesium concentrations fell below the reference range regularly in the citrate group and, when low, there was magnesium flux from dialysate to patient. Magnesium loss was greater in patients receiving citrate.
Exponential decline in magnesium concentrations was sufficiently rapid that subtherapeutic serum magnesium concentrations may occur well before detection when once-daily sampling was used. Measurements should be interpreted with regard to timing of magnesium infusions. We suggest that continuous renal replacement therapy fluids with higher magnesium concentrations be introduced in the critical care setting.
Available from: Zulfiqar Ahmad
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ABSTRACT: Nanomedicine results from nanotechnology where molecular scale minute precise nanomotors can be used to treat disease conditions. Many such biological nanomotors are found and operate in living systems which could be used for therapeutic purposes. The question is how to build nanomachines that are compatible with living systems and can safely operate inside the body? Here we propose that it is of paramount importance to have a workable base model for the development of nanomotors in nanomedicine usage. The base model must placate not only the basic requirements of size, number, and speed but also must have the provisions of molecular modulations. Universal occurrence and catalytic site molecular modulation capabilities are of vital importance for being a perfect base model. In this review we will provide a detailed discussion on ATP synthase as one of the most suitable base models in the development of nanomotors. We will also describe how the capabilities of molecular modulation can improve catalytic and motor function of the enzyme to generate a catalytically improved and controllable ATP synthase which in turn will help in building a superior nanomotor. For comparison, several other biological nanomotors will be described as well as their applications for nanotechnology.
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ABSTRACT: The aim of this study was to discern whether a relation between biochemical parameters, sonography and musculoskeletal data exists in cases of hyperthyroidism and whether they are modifiable through supplementation with selenomethionine and magnesium citrate as well as by acupuncture and manual medicine methods.ResultsA direct correlation between whole blood selenium and serum magnesium was found in subjects without thyroid disease and in menopausal women while it was reversed in cases of thyroid diseases as well as in patients with depression, infection, and in infertile women. Vascularization indices were elevated in cases of newly diagnosed benign thyroid diseases. Musculoskeletal changes i.e. lateral tension and idiopathic moving toes, as well as situations of physical and psychological stress and minor trauma and infection led to an increase of vascularization. Magnesium levels correlated negatively with these two conditions. The supplementation brought a reduction of the vascularization indices and reduced the incidence of idiopathic moving toes. Treatment of lateral tension required manual medicine methods and acupuncture (gastrocnemius). A small subgroup of patients showed a further reduction of hyper-vascularization after receiving coenzyme Q10.Conclusions
We interpret the elevated thyroid vascularization and low magnesium levels as signs of an inflammatory process related to the musculoskeletal changes. Improvement of thyroid function and morphology can be achieved after correcting the influence of stressors together with the supplementation regime. We hypothesize that the central biochemical event in thyroid disease is that of an acquired, altered mitochondrial function due to deficiency of magnesium, selenium, and coenzyme Q10.
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