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. 1981 May;67(5):985–989. doi: 10.1104/pp.67.5.985

Evidence of a Low Stromal Mg2+ Concentration in Intact Chloroplasts in the Dark

I. STUDIES WITH THE IONOPHORE A23187

Archie R Portis Jr 1,2
PMCID: PMC425814  PMID: 16661806

Abstract

The loss of Mg2+ upon the addition of the ionophore A23187 in the dark was prevented by less than 0.1 millimolar MgCl2 with intact chloroplasts suspended in a sorbitol medium, but required 1 to 3 millimolar MgCl2 if the chloroplasts were in a K+ -gluconate medium. Measurements of stromal pH in the dark indicated that, in the K+ -gluconate medium, the stromal pH is nearly the same as that of the medium, whereas in the sorbitol medium it is much more acidic as reported previously. These observations suggest that the free Mg2+ concentration in the stroma in the dark is between 1 and 3 millimolar. Other experiments on the inihibition by A23187 of CO2 fixation in the light and in a system capable of catalyzing CO2 fixation in the dark, and on the Mg2+ binding properties of thylakoid membranes, are consistent with this conclusion. The results provide further support for the hypothesis that light-induced Mg2+ concentration changes occur in the stroma that are important in the light-dark regulation of CO2 fixation.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. BURTON K. Formation constants for the complexes of adenosine di- or tri-phosphate with magnesium or calcium ions. Biochem J. 1959 Feb;71(2):388–395. doi: 10.1042/bj0710388. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Dilley R. A., Vernon L. P. Ion and water transport processes related to the light-dependent shrinkage of spinach chloroplasts. Arch Biochem Biophys. 1965 Aug;111(2):365–375. doi: 10.1016/0003-9861(65)90198-0. [DOI] [PubMed] [Google Scholar]
  3. Heldt H. W., Sauer F. The inner membrane of the chloroplast envelope as the site of specific metabolite transport. Biochim Biophys Acta. 1971 Apr 6;234(1):83–91. doi: 10.1016/0005-2728(71)90133-2. [DOI] [PubMed] [Google Scholar]
  4. Heldt W. H., Werdan K., Milovancev M., Geller G. Alkalization of the chloroplast stroma caused by light-dependent proton flux into the thylakoid space. Biochim Biophys Acta. 1973 Aug 31;314(2):224–241. doi: 10.1016/0005-2728(73)90137-0. [DOI] [PubMed] [Google Scholar]
  5. Hind G., Nakatani H. Y., Izawa S. Light-dependent redistribution of ions in suspensions of chloroplast thylakoid membranes. Proc Natl Acad Sci U S A. 1974 Apr;71(4):1484–1488. doi: 10.1073/pnas.71.4.1484. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Huber S. C., Maury W. Effects of Magnesium on Intact Chloroplasts: I. EVIDENCE FOR ACTIVATION OF (SODIUM) POTASSIUM/PROTON EXCHANGE ACROSS THE CHLOROPLAST ENVELOPE. Plant Physiol. 1980 Feb;65(2):350–354. doi: 10.1104/pp.65.2.350. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Jensen R. G., Bassham J. A. Photosynthesis by isolated chloroplasts. 3. Light activation of the carboxylation reaction. Biochim Biophys Acta. 1968 Jan 15;153(1):227–234. doi: 10.1016/0005-2728(68)90164-3. [DOI] [PubMed] [Google Scholar]
  8. Krause G. H. Light-induced movement of magnesium ions in intact chloroplasts. Spectroscopic determination with Eriochrome Blue SE. Biochim Biophys Acta. 1977 Jun 9;460(3):500–510. doi: 10.1016/0005-2728(77)90088-3. [DOI] [PubMed] [Google Scholar]
  9. Lehner K., Heldt H. W. Dicarboxylate transport across the inner membrane of the chloroplast envelope. Biochim Biophys Acta. 1978 Mar 13;501(3):531–544. doi: 10.1016/0005-2728(78)90119-6. [DOI] [PubMed] [Google Scholar]
  10. Lilley R. M., Chon C. J., Mosbach A., Heldt H. W. The distribution of metabolites between spinach chloroplasts and medium during photosynthesis in vitro. Biochim Biophys Acta. 1977 May 11;460(2):259–272. doi: 10.1016/0005-2728(77)90212-2. [DOI] [PubMed] [Google Scholar]
  11. Lilley R. M., Walker D. A. The reduction of 3-phosphoglycerate by reconstituted chloroplasts and by chloroplast extracts. Biochim Biophys Acta. 1974 Dec 19;368(3):269–278. doi: 10.1016/0005-2728(74)90174-1. [DOI] [PubMed] [Google Scholar]
  12. Pfeiffer D. R., Reed P. W., Lardy H. A. Ultraviolet and fluorescent spectral properties of the divalent cation ionophore A23187 and its metal ion complexes. Biochemistry. 1974 Sep 10;13(19):4007–4014. doi: 10.1021/bi00716a029. [DOI] [PubMed] [Google Scholar]
  13. Portis A. R., Jr, Chon C. J., Mosbach A., Heldt H. W. Fructose-and sedoheptulosebisphosphatase. The sites of a possible control of CO2 fixation by lightdependent changes of the stromal Mg2+ concentration. Biochim Biophys Acta. 1977 Aug 10;461(2):313–325. doi: 10.1016/0005-2728(77)90181-5. [DOI] [PubMed] [Google Scholar]

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