Oxidative Stress Induces Partial Degradation of the Large Subunit of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase in Isolated Chloroplasts of Barley

Abstract

The effects of oxidative stress on the degradation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) were studied in isolated chloroplasts from barley (Hordeum vulgare L. cv Angora). Active oxygen (AO) was generated by varying the light intensity, the oxygen concentration, or the addition of herbicides or ADP-FeCI,-ascorbate to the medium. Oxidative treatments stimulated association of Rubisco with the insoluble fraction of chloroplasts and partia1 proteolysis of the large subunit (LSU). The most prominent degradation product of the LSU of Rubisco showed an apparent molecular mass of 36 kD. The data suggest that an increase in the amount of AO photogenerated by O, reduction at photosystem I triggers Rubisco degradation. A possible relationship between AO-mediated denaturation of Rubisco and proteolysis of the LSU is discussed.

Senescence in wheat leaves: is a cysteine endopeptidase involved in the degradation of the large subunit of Rubisco?

“…Moreover, it has been reported by Navarre and Wolpert (1999) that in victorin-treated leaf slices, the formation of the 53 kDa fragment could be prevented in a similar manner by the addition of two different cysteine protease inhibitors (E-64 and leupeptin). In intact chloroplasts and chloroplast lysates, the most prominent cleavage products of LSU had molecular weights of about 36 and 16-kDa, but no 50 kDa product was described (Desimone et al 1996;Ishida et al 1997;Roulin and Feller 1998b). Degradation products of about 50 kDa could be detected in lysates only if chloroplasts were contaminated with vacuolar proteases (Miyadai et al 1990).…”

“…The most prominent degradation product of LSU in chloroplasts or their lysates had a molecular mass in the range of 36-37 kDa (Desimone et al 1996;Ishida et al 1997;Roulin and Feller 1998b). This fragment likely contains the N-terminus of Rubisco (Ishida et al 1997(Ishida et al , 1998Roulin and Feller 1998b), although another fragment without the N-terminus of LSU was mentioned by Desimone et al (1996). The direct cleavage of Rubisco in vitro by active oxygen species resulted in the formation of an N-terminal 37-kDa product and a 16-kDa fragment bearing the Cterminus (Ishida et al 1998(Ishida et al , 1999.…”

“…Since hydrolytic enzymes of the cytosol or the vacuole are spatially separated from plastidial proteins, it is tempting to suggest that plastidial proteins become degraded inside the chloroplast by plastidial peptide hydrolases (Brouquisse et al 2001;Hö rtensteiner and Feller 2002). Fragmentation of Rubisco has frequently been shown to occur in chloroplasts and chloroplast lysates Desimone et al 1996;Ishida et al 1997Ishida et al , 1998. A plastidial zinc protease able to hydrolyze Rubisco has been reported by Bushnell et al (1993).…”

“…A role for activated oxygen species in the degradation of Rubisco in intact chloroplasts seems likely. Both stimulation of Rubisco degradation under oxidative conditions (Desimone et al 1996;Roulin and Feller 1998b) and direct fragmentation of the enzyme by hydroxyl radicals (Ishida et al 1998) have been reported. The most prominent degradation product of LSU in chloroplasts or their lysates had a molecular mass in the range of 36-37 kDa (Desimone et al 1996;Ishida et al 1997;Roulin and Feller 1998b).…”

“…Both stimulation of Rubisco degradation under oxidative conditions (Desimone et al 1996;Roulin and Feller 1998b) and direct fragmentation of the enzyme by hydroxyl radicals (Ishida et al 1998) have been reported. The most prominent degradation product of LSU in chloroplasts or their lysates had a molecular mass in the range of 36-37 kDa (Desimone et al 1996;Ishida et al 1997;Roulin and Feller 1998b). This fragment likely contains the N-terminus of Rubisco (Ishida et al 1997(Ishida et al , 1998Roulin and Feller 1998b), although another fragment without the N-terminus of LSU was mentioned by Desimone et al (1996).…”