Thylakoid-Bound Proteolytic Activity vs. Exogenous AzocollSubstrate during Chloroplast Development in Bean

Involvement of nitric oxide in light-mediated greening of barley seedlings

“…In leaves left in the light in the presence of chlorophyll synthesis inhibitors (e.g. levulinic acid), the preaccumulated light harvesting complex of photosystem II (LHCII) was degraded (Anastassiou and Argyoudi-Akoyunoglou, 1995). Thus, chloroplastencoded reaction center proteins and LHCII apoproteins may compete for the limited amount of chlorophylls, which are required to anchor the proteins in the thylakoid membrane, rescuing them from degradation.…”

Thylakoid-bound proteolytic activity against LHC II apoprotein in bean

“…It is activated by Mg ++, its optimal pH is 8 and it is inhibited by EDTA. The proteolytic activity towards LHC II under photoinhibitory conditions was found to follow closely the photooxidation of Chl, suggesting that the Chl level may control the protease, just as our earlier work with the azocoll substrate suggested (Anastassiou and Argyroudi-Akoyunoglou 1995). This might explain why LHC II is degraded in the dark only in plants briefly preexposed to light (limited Chl accumulation) but not in those preexposed for prolonged time (Argyroudi- Akoyunoglou et al 1982;Akoyunoglou and Akoyunoglou 1985).…”

“…Thylakoid-bound proteolytic activity was detected in etiolated bean leaves during development in the dark or light (Anastassiou and Argyroudi-Akoyunoglou 1995). The activity, monitored by the azo-dye release from an insoluble azocoll substrate, followed closely the formation and growth of the photosynthetic units, suggesting that it may be involved in the control of the photosynthetic unit size.…”

“…These results implicate a degrading protease in the control of LHC II accumulation. Indeed, it has been found recently that thylakoids exhibit proteolytic activity vs. azocoll, an insoluble azo-dye-collagen complex, used as protease substrate; this activity seems to be regulated by the presence of Chl and the developmental stage of the plant in a way implying proteolytic regulation in the biogenesis of the photosynthetic units (Anastassiou and Argyroudi-Akoyunoglou 1995).…”