Modulation of endogenous protein phosphorylation in plant mitochondria by respiratory substrates

Abstract

Petit, P. X., Sommarin, M., Pical, C. and M0ller, I. M. 1990. Modulation of endogenous protein phosphorylation in plant mitochondria by respiratory substrates. Purified mitochondria from potato {Solanum tuberosum L. ev. Bintje) tubers were incubated with [y-'^F]-ATP, respiratory substrates and various effectors. The total incorporation of '^P into proteins was measured and the phosphoprotein pattern investigated by sodium dodecyl sulphate-polyacrylamide gel eleetrophoresis and autoradiography. Total incorporation was strongly reduced (by 70-80 %) by the respiratory substrates, succinate, pyruvate and NADH. The half-maximal inhibition was at 0.03, 0.3, and 0.3 mM, respectively. The labelling ofthe major phosphoproteins of 40 and 42 kDa (probably both the a-subtmit ofthe pyruvate dehydrogenase, EC 1.2.4.1) as well as of minor polypeptides of 26-33 kDa was reduced. A concomittant increase in the labelling of the 14 and 16 kDa bands occurred in the presence of succinate in fall but this increase could not be detected in late winter. The reduction' in total labelling caused by NADH and suecinate was unaffected by changes in the membrane potential (e.g. addition of uncouplers) or by inhibition of electron transport (e.g. by KCN). Malonate inhibition of succinate oxidation reversed the effects of succinate on labelling. The mechanism(s) by which respiratory substrates might affect protein kinase activity is discussed.

Protein phosphorylation/dephosphorylation in the inner membrane of potato tuber mitochondria

“…Sommarin et al [18] and Petit et al [9] showed that total 32 P incorporation into intact mitochondria reached a maximum incorporation after 1–2 min. A time course experiment on phosphorylation of inner membrane proteins showed that the maximum 32 P incorporation was reached only after 15–23 min [11].…”

“…Four inner membrane phosphoproteins have been identified by N‐terminal sequencing: the 18 kDa AQDQ subunit of complex I [3]; the 17 kDa subunit IV of cytochrome c oxidase [4]; and the 22 kDa δ′‐subunit and the 28 kDa β‐subunit of the F 0 F 1 ‐ATPase [5]. The phosphorylation of a number of unidentified proteins has also been demonstrated in bovine heart mitochondria [6,7] and in potato tuber mitochondria [5,8–10].…”

Protein phosphorylation in plant mitochondria

“…This inhibition was apparently not because of their oxidation as it was also observed when mitochondrial respiration was completely blocked by electron transport inhibitors. Likewise, the transmembrane proton gradient or the membrane potential did not appear to have a role in the regulation of PK activity in the mitochondria (Petit et al 1990).…”

NAD pattern and NADH oxidase activity in pea (Pisum sativum L.) under cadmium toxicity

“…It has been suggested that in some plant species, fully functional mitochondria are present in the dry seed (Attucci et al 1991), whereas in others, ATP synthesis is a product of fermentative pathways during the earliest stages of imbibitions (Raymond et al 1985). It has been shown that mitochondria in dry seeds rapidly became active during imbibition, relying on nicotinamide adenine dinucleotide phosphate-oxidase (NADH) as substrates (Petit et al 1990). In view of the fact that respiration is the driving force that powers germination, a high level of mitochondrial stress tolerance certainly contributes to the vigor of germinating seeds in the environment (Logan et al 2001).…”