scholarly journals Reconstitution of Photosynthetic Energy Conservation. II. Photophosphorylation in Liposomes Containing Photosystem-I Reaction Center and Chloroplast Coupling-Factor Complex

1980 ◽  
Vol 111 (2) ◽  
pp. 535-543 ◽  
Author(s):  
Gunter HAUSKA ◽  
Dietrich SAMORAY ◽  
Gabriele ORLICH ◽  
Nathan NELSON
Keyword(s):  
Energy Conservation ◽  
Reaction Center ◽  
Photosystem I ◽  
Coupling Factor ◽  
Chloroplast Coupling Factor

scholarly journals A direct interaction between Photosystem I and the chloroplast coupling factor

1986 ◽  
Vol 234 (1) ◽  
pp. 217-220 ◽  
Author(s):  
B Huchzermeyer ◽  
A Loehr ◽  
I Willms
Keyword(s):  
Photosystem I ◽  
Binding Sites ◽  
Protein Complexes ◽  
Electron Transport Rate ◽  
Direct Interaction ◽  
Coupling Factor ◽  
Primary Result ◽  
Regulatory Effect ◽  
Experimental Conditions ◽  
Chloroplast Coupling Factor

A regulation of the ATP-synthesizing complex by electron-transport rate has been found. The site of regulation could be localized within the Photosystem I region. The regulatory effect probably is produced by direct interactions between neighbouring charged protein complexes. The primary result is an increase in the percentage of those binding sites adopting a low-affinity state. This seems to lead to an enhanced leakage of protons out of the thylakoids, especially under those experimental conditions employing low nucleotide concentrations. Changes in the P/2e ratio can be observed, especially if the total ADP + ATP concentration used in the experiment is below 200 microM.

Phosphate Binding to Isolated Chloroplast Coupling Factor (CF1)

1988 ◽  
Vol 43 (3-4) ◽  
pp. 213-218 ◽  
Author(s):  
Bernhard Huchzermeyer
Keyword(s):  
Atpase Activity ◽  
Binding Site ◽  
Inorganic Phosphate ◽  
Coupling Factor ◽  
Binding Domain ◽  
Atp Binding ◽  
Phosphate Binding ◽  
Chloroplast Coupling Factor ◽  
Single Binding Site ◽  
Site Binding

A single binding site for phosphate was found on isolated chloroplast coupling factor in the absence of nucleotides. In our experiments the phosphate binding site showed a Kd of 170 μᴍ. We did not observe any differences whether the ATPase activity of CF] had been activated or not. If the enzyme was incubated with [γ-32P]ATP the amount of 32P bound per CF1 depended on the pretreatment of the enzyme: In the presence of ADP no ATP or phosphate was bound to CF,. After activation of ATPase activity one mol of ATP per mol CF, was rapidly bound and hydrolyzed while there was a slowly occurring binding of another phosphate without concomitant nucleotide binding. We conclude that there are two different types of phosphate binding observed in our experiments: 1) Inorganic phosphate can be bound by one catalytic site per mol of CF1 2) The γ-phosphate of ATP is able to bind to an ATP binding domain of the enzyme if this domain can exchange substrates with the incubation medium. This ATP binding domain appears to differ from the site binding inorganic phosphate, because at least a portion of the coupling factor contains more than one labelled phosphate during our ATPase tests.

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