On the relationship between matrix free Mg2+ concentration and total Mg2+ in heart mitochondria
| Autor: | Edward S. Panzeter, Kemal Baysal, Dennis W. Jung, Gerald P. Brierley |
|---|---|
| Rok vydání: | 1997 |
| Předmět: |
inorganic chemicals
Nigericin Fura-2 Stereochemistry Potassium Cell Respiration Biophysics chemistry.chemical_element Furaptra Mersalyl Biochemistry Mitochondria Heart Mg2+ metabolism Phosphates chemistry.chemical_compound Mitochondrial Mg2+ Animals Magnesium Enzyme Inhibitors Inner mitochondrial membrane Magnesium ion Heart metabolism Fluorescent Dyes Membrane potential Binding Sites Ionophores Chemistry Biological Transport Cell Biology Mitochondria Spectrometry Fluorescence Cattle Mitochondrial Swelling |
| Zdroj: | Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1320(3):310-320 |
| ISSN: | 0005-2728 |
| DOI: | 10.1016/s0005-2728(97)00036-4 |
| Popis: | The matrix free magnesium ion concentration, [Mg2+]m, estimated using the fluorescent probe furaptra, averaged 0.67 mM in 15 preparations of beef heart mitochondria containing an average of 21 nmol total Mg2+ per mg protein. [Mg2+]m was compared with total Mg2+ during respiration-dependent uptake and efflux of Mg2+ and during osmotic swelling. In the absence of external Pi these mitochondria contain about 32 nmol/mg non-diffusible Mg-binding sites with an apparent Kd of 0.34 mM. [Mg2+]m depends on both the size of the total Mg2+ pool and the ability of matrix anions to provide Mg-ligands. Pi interacts strongly with Mg2+ to decrease [Mg2+]m and, in the absence of external Mg2+, promotes respiration-dependent Mg2+ efflux and a decrease in [Mg2+]m to very low levels. The uptake of Pi by respiring mitochondria converts delta pH to membrane potential (delta psi) and provides additional Mg-binding sites. This permits large accumulations of Mg2+ and Pi with little change in [Mg2+]m. Nigericin also converts delta pH to delta psi in respiring mitochondria and induces a large and rapid increase in both total Mg2+ and [Mg2+]m. Mersalyl increases the permeability of the mitochondrial membrane to cations and this also induces a marked increase in both total Mg2+ and [Mg2+]m. These results suggest that mitochondria take up Mg2+ by electrophoretic flux through membrane leak pathways, rather than via a specific Mg2+ transporter. Mitochondria swollen by respiration dependent uptake of potassium phosphate show decreased [Mg2+]m, whereas those swollen to the same extent in potassium acetate do not. This suggests that [Mg2+]m is well-buffered during osmotic volume changes unless there is also a change in ligand availability. |
| Databáze: | OpenAIRE |
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