Etioplasts coupling factor

Etioplasts Contain a Coupling Factor for Photosynthetic Phosphorylation... 

First, it was necessary to see if mature green-maize chloroplast membranes were coated with 90-A particles. Thylakoids were prepared and examined by negative staining in the electron microscope. On the surface of these membranes, we could see 90 A-particles, similar to those on spinach thylakoids and on maize etioplast membranes. This supported our opinion that the 90-A particles in etioplast membranes are identical to the coupling factor. However, some additional experiments were necessary to demonstrate this. 

This demonstration that etioplast membranes contain many coupling factor particles indicates that a unit of assembly of these membranes is not the same as a unit of function. The presence of these particles also shows that there must be sites for their association which are built into the membrane, although it lacks chlorophyll and, as will be shown, many other components necessary for photosynthesis. 

M NaCl-0.15 mM EDTA and collecting the membranes by centrifugation. The stripped membranes could not carry on A/B phosphorylation. The capacity to do this was, however, restored by incubating coupling-factor preparations from chloropiasts or etioplasts of maize with stripped thylakoids in 0.01 m EDTA-0.1 m MgCl2. This showed that the CFi was required, but was probably not the limiting factor since it is present in etioplasts. What other conditions are required ... 

Maize etioplasts, as chloropiasts, have coupling factor particles. What about their osmotic integrity Are there closed vesicles in etioplast membrane preparations This question was examined experimentally by de-... 

Fig. 6. Osmotic response and A/B phosphorylation of thylakoid and etioplast membranes in media of varying sucrose concentrations. Green A/B A/B phosphorylation of thylakoids. Etiolated A/B no detectable A/B phosphorylation in etioplast membranes. Green PPV osmotic response of thylakoid membranes. Etiolated PPV osmotic response of etioplast membranes. Green EDTA/PPV osmotic response of thylakoids extracted with EDTA-NaCl to remove coupling factor. The packed pellet volume in sucrose-free solution was taken as 100%. A/B activity was measured by assaying the amount of Pi incorporated into ATP. (From Forger and Bogorad. )...

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