Diversification of isoelectric points from isolated chloroplasts during the cell cycle of Euglena gracilis, strain z

Abstract

We describe a rapid method whereby isolated chloroplasts from Euglena gracilis can be separated in a Ficoll gradient according to their surface pK's by isoelectric focusing in one hour or less. The linear Ficoll gradient is made isotonic over the whole separation distance by addition of sucrose. No released proteins of the isolated chloroplasts are detectable after isoelectric focusing. Modifications of the chloroplast envelope during the cell cycle of Euglena gracilis are evident by alterations of their isoelectric points.

Cooperation of Cytoplasmic and Plastidial Translation in Formation of the Photosynthetic Apparatus and Its Stage-Specific Efficiency

“…The regulation between synthesis of LHCP precursor proteins in the cytoplasm and their insertion simultaneous with CPa proteins into the thylakoids is beyond the scope of this paper. It should be mentioned, however, that at 6 LH the polypeptide composition and the surface pK of the chloroplast envelopes in synchronized E. gracilis is quite different from the other development stages (7,8). This might be a prerequisite for the entry of LHCP precursor proteins into the Euglena chloroplasts.…”

“…The biogenesis of Euglena chloroplasts is a complicated, highly organized, and well-regulated process (3-9, 15, 21) which is dependent on both chloroplast and cytoplasmic protein synthesis (5)(6)(7)(8). It is clear that the formation of thylakoids in Euglena chloroplasts requires the integrated activities of both translation systems.…”

“…The syntheses sequence of the chlorophyll-protein-complexes coincides with the efficiency alterations of the photosynthetic apparatus of E. gracis during the light period of the cell cycle. In particular, the synthesis onset of the photosystem II-related polypeptides CPa and LHCP aligns with the decrease of oxygen evolution at 6 hours of the light period and is discussed as reorganization process in the thylakoids.The biogenesis of Euglena chloroplasts is a complicated, highly organized, and well-regulated process (3-9, 15, 21) which is dependent on both chloroplast and cytoplasmic protein synthesis (5)(6)(7)(8). It is clear that the formation of thylakoids in Euglena chloroplasts requires the integrated activities of both translation systems.…”