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Phosphate transport and proteins with SH groups in rat liver mitochondria
Abstract:
Phosphate transport in rat liver mitochondria was studied by following [32P] phosphate uptake within physiological concentrations. Transport inhibition due to mersalyl and protection by mersalyl against N-ethylmaleimide measured in those conditions corresponded to earlier results obtained by the swelling technique. When mitochondria were incubated with [3H] N-ethylmaleimide in the presence of mersalyl, the radioactive labeling in proteins of particles obtained after sonication was decreased in all fractions, but three proteins were both highly alkylated and also highly protected by mersalyl (M.W. 48,000 - 36,000 - 31,000). Two of these (M.W. 36,000 and 31,000) were partially purified by ultrogel chromatography in the presence of sodium dodecyl sulfate. Furthermore, it was shown that both phosphate and nigericin diminished labeling by N-ethylmaleimide in the final supernatant fraction. Two proteins (M.W. 98,000 and 31,000) were significantly alkylated by [3H] N-ethylmaleimide and protected by phosphate and nigericin.
Insights
This study investigated phosphate transport in rat liver mitochondria, identifying specific proteins involved in the process. Researchers found that phosphate and nigericin protect certain mitochondrial proteins from N-ethylmaleimide labeling.
Area of Science:
- Mitochondrial physiology
- Biochemistry
- Cellular transport mechanisms
Background:
- Phosphate transport is crucial for cellular energy metabolism.
- Understanding mitochondrial phosphate transport is key to cellular function.
- Previous studies utilized swelling techniques to investigate this process.
Purpose of the Study:
- To elucidate the molecular mechanisms of phosphate transport in rat liver mitochondria.
- To identify proteins involved in phosphate transport using radiolabeling techniques.
- To investigate the interaction of transport inhibitors and protectors with mitochondrial proteins.
Main Methods:
- Studied [32P] phosphate uptake in rat liver mitochondria at physiological concentrations.
- Utilized [3H] N-ethylmaleimide for protein alkylation and mersalyl for inhibition studies.
- Employed sonication, ultrogel chromatography, and sodium dodecyl sulfate for protein analysis.
- Measured the effect of phosphate and nigericin on N-ethylmaleimide labeling.
Main Results:
- Mersalyl inhibited phosphate transport and protected against N-ethylmaleimide, consistent with prior findings.
- Three proteins (M.W. 48,000, 36,000, and 31,000) were highly alkylated and protected by mersalyl.
- Two proteins (M.W. 36,000 and 31,000) were partially purified.
- Phosphate and nigericin reduced N-ethylmaleimide labeling in the supernatant, affecting M.W. 98,000 and 31,000 proteins.
Conclusions:
- Identified specific mitochondrial proteins (M.W. 36,000 and 31,000) likely involved in phosphate transport.
- Demonstrated that phosphate and nigericin modulate the interaction of N-ethylmaleimide with mitochondrial proteins.
- Provided insights into the molecular targets of transport inhibitors and protectors in mitochondrial phosphate transport.