The stoichiometry of the chloroplast ATP synthase oligomer III in Chlamydomonas reinhardtii is not affected by the metabolic state

Abstract

The chloroplast H(+)-ATP synthase is a key component for the energy supply of higher plants and green algae. An oligomer of identical protein subunits III is responsible for the conversion of an electrochemical proton gradient into rotational motion. It is highly controversial if the oligomer III stoichiometry is affected by the metabolic state of any organism. Here, the intact oligomer III of the ATP synthase from Chlamydomonas reinhardtii has been isolated for the first time. Due to the importance of the subunit III stoichiometry for energy conversion, a gradient gel system was established to distinguish oligomers with different stoichiometries. With this methodology, a possible alterability of the stoichiometry in respect to the metabolic state of the cells was examined. Several growth parameters, i.e., light intensity, pH value, carbon source, and CO(2) concentration, were varied to determine their effects on the stoichiometry. Contrary to previous suggestions for E. coli, the oligomer III of the chloroplast H(+)-ATP synthase always consists of a constant number of monomers over a wide range of metabolic states. Furthermore, mass spectrometry indicates that subunit III from C. reinhardtii is not modified posttranslationally. Data suggest a subunit III stoichiometry of the algae ATP synthase divergent from higher plants.

Metabolism controls dimerization of the chloroplast FoF1 ATP synthase in Chlamydomonas reinhardtii

“…Besides photosynthesis (photoautotrophic growth) the cell is able to metabolize organic substrates such as acetate for heterotrophic nutrition, or both at the same time (photomixotrophic growth). The two different growth conditions applied, photomixotrophic and photoautotrophic growth, have a pronounced influence on the metabolic state of the cell, as previously shown [17]. Cells grow faster in the presence of acetate, they contain more protein per cell [17], and the composition of photosynthetic supercomplexes change.…”

“…The two different growth conditions applied, photomixotrophic and photoautotrophic growth, have a pronounced influence on the metabolic state of the cell, as previously shown [17]. Cells grow faster in the presence of acetate, they contain more protein per cell [17], and the composition of photosynthetic supercomplexes change. In photoautotrophically grown cells, two species of Photosystem I occur, only one species is found in photomixotrophically grown cells [18].…”

“…In our second experimental approach, employing stable isotope labeling to monitor the ratio of monomeric to dimeric CF o F 1 , the absolute protein amount of the two cell cultures, which can be and is quite different under the two culture conditions applied [17], does not affect the interpretation of the results. The isotope labeling approach leads in general to a more reliable quantification than the standard approach, since artifacts due to separate biochemical treatment and data evaluation ( Figs.…”

“…Photomixotrophic grown algal cultures exhibit significantly higher growth rates than photoautotrophic ones [17,18]. Since acetate is metabolized in photomixotrophic growth, mitochondrial metabolism and ATP production should increase on the expense of ATP production by chloroplasts.…”

The Oligomeric State of c Rings from Cyanobacterial F-ATP Synthases Varies from 13 to 15

“…A number of c-ring preparations from various species revealed a remarkable flexibility in the c-ring stoichiometry, ranging from 10 subunits in Saccharomyces cerevisiae (36), Escherichia coli (12), and Bacillus sp. strain PS3 (23); 11 subunits in I. tartaricus (35), Propionigenium modestum (19), and Clostridium paradoxum (18); and 14 subunits in chloroplasts (22,34) to 15 subunits in the alkaliphilic cyanobacterium Arthrospira sp. strain PCC 9438 (28).…”