Article

Planta

, Volume 205, Issue 3, pp 459-466

Degradation of active-oxygen-modified ribulose-1,5-bisphosphate carboxylase/oxygenase by chloroplastic proteases requires ATP-hydrolysis

  • Marcelo DesimoneAffiliated withInstitut für Biologie II, Universität Freiburg, Schänzlestr. 1, D-79104 Freiburg, Germany
  • , Edgar WagnerAffiliated withInstitut für Biologie II, Universität Freiburg, Schänzlestr. 1, D-79104 Freiburg, Germany
  • , Udo JohanningmeierAffiliated withInstitut für Biologie II, Universität Freiburg, Schänzlestr. 1, D-79104 Freiburg, Germany

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Abstract.

Active oxygen (AO) species generated in plants under stress conditions trigger degradation of Rubisco (EC 4.1.1.39). To find out whether AO species activate proteases or make the protein susceptible to proteolysis, purified and 14C-labelled Rubisco protein was incubated with stromal preparations obtained from barley (Hordeum vulgare L.) leaves. The protein was degraded into distinct fragments only after a treatment with AO. This result shows that AO-treated Rubisco has been modified to become a substrate for stromal protease(s) and dismisses the possibility of protease activation. Upon degradation, distinct fragments accumulated with time. The fragmentation pattern was indistinguishable from that obtained with intact chloroplasts subjected to oxidative conditions (cf. M. Desimone et al., 1996, Plant Physiol 111: 789–796). Degradation required ATP-hydrolysis, since AMP, ADP or non-hydrolysable ATP-analogs did not support proteolysis. The ClpP-deficient stromal preparations degraded AO-modified Rubisco, making the involvement of the ClpC/P protease unlikely.

Key words: Active oxygen ATP-dependent proteoly-sis Hordeum Protein degradation Ribulose-1 5-bisphosphate carboxylase/oxygenase Stroma (chloroplast protease)