Reversal of Copper Inhibition in Chloroplast Reactions by Manganese

Habermann, Helen M.

doi:10.1104/pp.44.3.331

Cited by 33 publications

(27 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As a means of exploring where within photosystem II in- DISCUSSION In studying the effects of Cu2+ on electron transport of isolated chloroplasts it was found not only that the concentration of the inhibitor was important in determining the degree of inhibition, but that the ratio of chloroplasts to inhibitor, as well as preincubation, must also be considered-facts overlooked in previous studies (5,10). Steemann-Nielsen et al (16) studying the effect of Cu2+ on photosynthesis of whole algal cells noticed that the ratio of cells to inhibitor was one of the most important factors determining the degree of inhibition obtained.…”

Section: Resultsmentioning

confidence: 99%

“…Haberman (5) observed that exogenous Mn2+ reduced the degree of Cu2`inhibition in several kinds of chloroplast-mediated reactions and postulated that Cu2' affects the site of manganese action; however, this could be due to Mn'+ stimulating electron transport. In fact, her data show a marked increase in the rate of electron transport when Mn2+ was included in the reaction media.…”

Section: Resultsmentioning

confidence: 99%

“…The normal reaction media for studying 02 evolution had the following composition in a total volume of 2 ml: 50 mm HEPES, pH 7.6; 10 mM KCl; 5 …”

Section: Methodsmentioning

confidence: 99%

“…In addition, Haberman (5) using chloroplasts from Phytolacca americanca showed that both the Hill and Mehler reactions were inhibited by Cu2+ but that the Mehler reaction was inhibited by lower concentrations of the ion.…”

mentioning

confidence: 99%

“…Cupric sulfate has been extensively used as an algaecide since the beginning of the century (12). The cupric ion has been shown to be an inhibitor of photosynthesis in algal cells (4,11,16) and to inhibit photosynthetic electron transport in isolated chloroplasts (5,10).…”

mentioning

confidence: 99%

See 4 more Smart Citations

The Cupric Ion as an Inhibitor of Photosynthetic Electron Transport in Isolated Chloroplasts

1972

View full text Add to dashboard Cite

The role of copper in photosynthetic organisms depends greatly on its concentration. Copper, as cupric ion, in trace amounts is an essential micronutrient for algae and higher plants (17,20) and is an essential constituent of several enzymes such as polyphenol oxidase (3) and plastocyanin (8), a component of photosynthetic electron transport. Concentrations higher than 1 /tm are increasingly toxic to algal and higher plant tissues (4, 13). Cupric sulfate has been extensively used as an algaecide since the beginning of the century (12). The cupric ion has been shown to be an inhibitor of photosynthesis in algal cells (4,11,16) and to inhibit photosynthetic electron transport in isolated chloroplasts (5, 10).The mechanism by which the Cu'+ inhibits the photosynthetic apparatus has been only partially elucidated thus far. The data on inhibition of photosynthesis in isolated chloroplasts gives an incomplete picture of the specific sites of inhibition in the electron transport chain. Macdowall (10) He studied the effect of light intensity on inhibition and concluded that the light reactions were directly affected by Cu21. In addition, Haberman (5) using chloroplasts from Phytolacca americanca showed that both the Hill and Mehler reactions were inhibited by Cu2+ but that the Mehler reaction was inhibited by lower concentrations of the ion.In contrast to Macdowall, Haberman concluded that Cu2+ was inhibiting a dark reaction and did not alter the reactions associated with the photoacts. She observed that Mn2+ added at a concentration of 0.5 mm reduced the inhibition of chloroplasts by Cu2+ and postulated that the Cu2+ was affecting the site of manganese function in 02 evolution. Recently exogenous Mn2+ has been shown to donate electrons after the water oxidation site of photosystem II of isolated chloroplasts (2), suggesting that, at high concentrations, manganese functions in a way other than its primary role in the water oxidation act.This work was conducted with the purpose of resolving the sites of Cu2+ inhibition in photosynthetic electron transport. Since previous work and our preliminary experiments pointed to the fact that photosystem II is preferentially inhibited by Cu2+ emphasis was given to finding the specific sites of inhibition within this photosystem. MATERIALS AND METHODSChloroplasts were prepared from market-grown spinach (Spinacia olercacea L.) as described by Robinson and Stocking (14). MnCl2 was excluded from the grinding and resuspending media in the preparations where Mn2+ was used as an electron donor. Chlorophyll was determined by the method of Arnon (1). Ferredoxin was isolated by the method of San Pietro (15) as modified by Swader and Jacobson (18). The 02 evolving capacity of the chloroplasts was destroyed by a mild heat treatment as described by Hinkson and Vernon (6). The chloroplasts were uncoupled by adding ammonium ions following the principle discovered by Krogman et al. (9).The normal reaction media for studying 02 evolution had the following composition in a total volume of 2...

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

“…The normal reaction media for studying 02 evolution had the following composition in a total volume of 2 ml: 50 mm HEPES, pH 7.6; 10 mM KCl; 5 …”

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%