| | 1 | Author
| E. B. Racht, A. Trebst | Requires cookie* | | | Title
| Hypothesis on the Control of D 1 Protein Turnover by Nuclear Coded Proteins in Chlamydomonas reinhardtii  | | | | Abstract
| A hypothesis is presented on the events in the degradation of the D 1 protein of photosys tem II in the light. It proposes the existence of a nuclear encoded cleavage system that is turning over and which is m odulated by its phosphorylation state. A new experimental ap proach is presented in which the D 1 protein degradation under photoinhibitory light is tested in Chlam ydom onas reinhardtii grown under phosphate deficiency and pretreated with cyclo-heximide. Under these conditions the degradation of the D 1 protein is delayed whereas in C hlam y dom onas reinhardtii grown in full medium the D 1 protein is rapidly disappearing in high light upon addition o f chloramphenicol (CAP) or lincomycin for inhibiting the resynthesis of the D 1 protein . Cycloheximide (C H I) has little effect on photoinhibition in such control cells. In cells grown, however, for 20 h in phosphate deficiency -such that there is not yet loss of photosynthesis capacity -pretreatment with cycloheximide or canavanine in low light the degradation of the D 1 protein even in 6 h high light is prevented to an appreciable extent. Further addition of CAP or lincomycin has only a small effect. [14C]leucine incorporation was used to show that there is no resynthesis and that the presence of the D 1 protein is due to a delay of degradation. The results are interpreted to show that excess high light which converts the D 1 protein into a potentially, degradable m ode is not sufficient for degradation of the D 1 protein. A cleavage system is needed as well. It is postulated that under phosphate deficiency and pre treatment with CHI or canavanine a nuclear coded cleavage system for the D 1 protein is depleted, i.e. the cleavage system for the rapidly turning over D 1 is also turning over. It is shown that under phosphate deficiency an alkaline phosphatase activity in the chloro plast and the thylakoid membrane o f Chlam ydom onas reinhardtii is increased. It is proposed that the ratio of kinase/phosphatase converts an active, stable phosphorylated cleavage system into a labile unphosphorylated and turning over state. | | | |
Reference
| Z. Naturforsch. 49c, 439 (1994); received January 31/May 13 1994 | | | |
Published
| 1994 | | | |
Keywords
| Chlamydomonas, D 1 Protein, Photoinhibition, Photosystem II, Phosphate Deficiency | | | |
Similar Items
| Find | | | DEBUG INFO
| | | | | TEI-XML for
| default:Reihe_C/49/ZNC-1994-49c-0439.pdf | | | | Identifier
| ZNC-1994-49c-0439 | | | | Volume
| 49 | |
|
