POSSIBLE PARTICIPATION OF MEMBRANE PHOSPHOPROTEINS IN THE CONTROL OF THE INTERACTION OF LIGHT PROCESSES AND CARBON METABOLISM

The effect of membrane protein phosphorylation on the excitation spect ra of the long-wavelength fluorescence of isolated chloroplasts was in vestigated in two maize inbreds, These fluorescence data are compared with the effects of protein phosphorylation on the rates of cyclic and noncyclic electron transfer within PS I, the rates of CO2 assimilatio n, and the composition of the products of dark photosynthetic processe s. Phosphoproteins were shown to selectively interact with two antenna complexes of PS I (F720 and F735), the character of the interaction v arying between the two maize lines. The cyclic and noncyclic electron transfer in PS I were shown to be differentially activated by the prot ein phosphorylation. This activation was due to an enhanced excitation energy transfer caused by a selective binding of phosphoproteins to t he antenna complexes F720 and F735. CO2 fixation rates and the pattern s of C-14-labeling of photosynthates differed between the two maize li nes. It is concluded that, as shown previously in pea chloroplasts, se lective interaction of phosphoproteins with two different antennae of PS I in maize chloroplasts results in a differential enhancement of cy clic and noncyclic electron flows. Products of dark photosynthetic car bon metabolism differed in the two maize lines, in which cyclic and no ncyclic electron transfer were differentially activated upon membrane protein phosphorylation.